meson: deprecated 'true' and 'false' in combo options for 'enabled' and 'disabled'

To prepare to use meson's builtin feature options in the future, which
are more powerful and provide useful feature for packagers, like the
ability to turn all "automagic" features off, and then explicitly turn
on the ones they want.

This is designed to make the transition softer, since the 'true' and
'false' are still accepted, just with a warning.

Acked-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4740>
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 21f464c..2e4290d 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -218,7 +218,7 @@
     - arm_test
 
 # Native Windows docker builds
-# 
+#
 # Unlike the above Linux-based builds - including MinGW/SCons builds which
 # cross-compile for Windows - which use the freedesktop ci-templates, we
 # cannot use the same scheme here. As Windows lacks support for
@@ -250,7 +250,7 @@
     - mesa
   script:
     - .\.gitlab-ci\windows\mesa_container.ps1 $CI_REGISTRY $CI_REGISTRY_USER $CI_REGISTRY_PASSWORD $WINDOWS_IMAGE $WINDOWS_UPSTREAM_IMAGE
-  
+
 .use-windows_build_vs2019:
   extends: .windows-docker-vs2019
   image: "$WINDOWS_IMAGE"
@@ -323,14 +323,14 @@
     - .meson-build
     - .ci-deqp-artifacts
   variables:
-    UNWIND: "true"
+    UNWIND: "enabled"
     DRI_LOADERS: >
       -D glx=dri
-      -D gbm=true
-      -D egl=true
+      -D gbm=enabled
+      -D egl=enabled
       -D platforms=x11,drm,surfaceless
     GALLIUM_ST: >
-      -D dri3=true
+      -D dri3=enabled
     GALLIUM_DRIVERS: "swrast,virgl"
     VULKAN_DRIVERS: amd
     BUILDTYPE: "debugoptimized"
@@ -343,20 +343,20 @@
 meson-gallium:
   extends: .meson-build
   variables:
-    UNWIND: "true"
+    UNWIND: "enabled"
     DRI_LOADERS: >
       -D glx=dri
-      -D gbm=true
-      -D egl=true
+      -D gbm=enabled
+      -D egl=enabled
       -D platforms=x11,wayland,drm,surfaceless
     GALLIUM_ST: >
-      -D dri3=true
+      -D dri3=enabled
       -D gallium-extra-hud=true
-      -D gallium-vdpau=true
-      -D gallium-xvmc=true
+      -D gallium-vdpau=enabled
+      -D gallium-xvmc=enabled
       -D gallium-omx=bellagio
-      -D gallium-va=true
-      -D gallium-xa=true
+      -D gallium-va=enabled
+      -D gallium-xa=enabled
       -D gallium-nine=true
       -D gallium-opencl=disabled
     GALLIUM_DRIVERS: "iris,nouveau,kmsro,r300,r600,freedreno,swr,swrast,svga,v3d,vc4,virgl,etnaviv,panfrost,lima,zink"
@@ -370,11 +370,11 @@
 meson-classic:
   extends: .meson-build
   variables:
-    UNWIND: "true"
+    UNWIND: "enabled"
     DRI_LOADERS: >
       -D glx=dri
-      -D gbm=true
-      -D egl=true
+      -D gbm=enabled
+      -D egl=enabled
       -D platforms=x11,wayland,drm,surfaceless
     DRI_DRIVERS: "auto"
     EXTRA_OPTION: >
@@ -386,20 +386,20 @@
     - .meson-build
   stage: meson-misc
   variables:
-    UNWIND: "false"
+    UNWIND: "disabled"
     DRI_LOADERS: >
       -D glx=disabled
-      -D gbm=false
-      -D egl=true
+      -D gbm=disabled
+      -D egl=enabled
       -D platforms=surfaceless
       -D osmesa=none
     GALLIUM_ST: >
-      -D dri3=false
-      -D gallium-vdpau=false
-      -D gallium-xvmc=false
+      -D dri3=disabled
+      -D gallium-vdpau=disabled
+      -D gallium-xvmc=disabled
       -D gallium-omx=disabled
-      -D gallium-va=false
-      -D gallium-xa=false
+      -D gallium-va=disabled
+      -D gallium-xa=disabled
       -D gallium-nine=false
     LLVM_VERSION: "8"
 
@@ -422,7 +422,7 @@
     CROSS: armhf
     LLVM_VERSION: "7"
     EXTRA_OPTION: >
-      -D llvm=false
+      -D llvm=disabled
   script:
     - .gitlab-ci/meson-build.sh
     - .gitlab-ci/prepare-artifacts.sh
@@ -434,7 +434,7 @@
   variables:
     VULKAN_DRIVERS: "freedreno"
     EXTRA_OPTION: >
-      -D llvm=false
+      -D llvm=disabled
   script:
     - .gitlab-ci/meson-build.sh
     - .gitlab-ci/prepare-artifacts.sh
@@ -451,7 +451,7 @@
 meson-clang:
   extends: .meson-build
   variables:
-    UNWIND: "true"
+    UNWIND: "enabled"
     DRI_LOADERS: >
       -D glvnd=true
     DRI_DRIVERS: "auto"
@@ -478,18 +478,18 @@
 meson-clover:
   extends: .meson-build
   variables:
-    UNWIND: "true"
+    UNWIND: "enabled"
     DRI_LOADERS: >
       -D glx=disabled
-      -D egl=false
-      -D gbm=false
+      -D egl=disabled
+      -D gbm=disabled
     GALLIUM_ST: >
-      -D dri3=false
-      -D gallium-vdpau=false
-      -D gallium-xvmc=false
+      -D dri3=disabled
+      -D gallium-vdpau=disabled
+      -D gallium-xvmc=disabled
       -D gallium-omx=disabled
-      -D gallium-va=false
-      -D gallium-xa=false
+      -D gallium-va=disabled
+      -D gallium-xa=disabled
       -D gallium-nine=false
       -D gallium-opencl=icd
   script:
@@ -505,11 +505,11 @@
     - meson-clover
     - .use-x86_build_old
   variables:
-    UNWIND: "false"
+    UNWIND: "disabled"
     DRI_LOADERS: >
       -D glx=disabled
-      -D egl=false
-      -D gbm=false
+      -D egl=disabled
+      -D gbm=disabled
       -D platforms=drm,surfaceless
     GALLIUM_DRIVERS: "i915,r600"
   script:
@@ -520,20 +520,20 @@
 meson-vulkan:
   extends: .meson-build
   variables:
-    UNWIND: "false"
+    UNWIND: "disabled"
     DRI_LOADERS: >
       -D glx=disabled
-      -D gbm=false
-      -D egl=false
+      -D gbm=disabled
+      -D egl=disabled
       -D platforms=x11,wayland,drm
       -D osmesa=none
     GALLIUM_ST: >
-      -D dri3=true
-      -D gallium-vdpau=false
-      -D gallium-xvmc=false
+      -D dri3=enabled
+      -D gallium-vdpau=disabled
+      -D gallium-xvmc=disabled
       -D gallium-omx=disabled
-      -D gallium-va=false
-      -D gallium-xa=false
+      -D gallium-va=disabled
+      -D gallium-xa=disabled
       -D gallium-nine=false
       -D gallium-opencl=disabled
       -D b_sanitize=undefined
@@ -589,11 +589,11 @@
   extends: .meson-build
   stage: meson-misc
   variables:
-    UNWIND: "false"
+    UNWIND: "disabled"
     DRI_DRIVERS: ""
     GALLIUM_DRIVERS: "swrast"
     EXTRA_OPTION: >
-      -Dllvm=false
+      -Dllvm=disabled
       -Dosmesa=gallium
       --cross-file=.gitlab-ci/x86_64-w64-mingw32