egl/x11: Implement dri3 support with loader's dri3 helper

v2: From Martin Peres
 - Tell we are compiling the dri3 backend in configure.ac
 - Update the Makefile.am
 - get rid of the LIBDRM_HAS_RENDERNODE_SUPPORT macro
 - fix some warnings related to EGLuint64KHR to int64_t conversions
 - use dri2_get_dri_config to get the __DRIconfig instead of open-coding it
 - replace the occasional tabs with spaces

v3: From Martin Peres
 - fix and indent problem (Matt Turner)
 - drop the authenticate function, use NULL in the vtable instead (Emil)
 - drop some useless includes (Emil Velikov)
 - mandate libdrm (Emil Velikov)
 - link to xcb-dri3 (Kristian Høgsberg)
 - convert to the new loader interface for drwable (Kristian)
 - remove some dead code after the dropping of some vfuncs (Kristian)
 - add a comment on the topic of rendering to the frontbuffer

v4: From Martin Peres
 - do not expose the preserved swap behavior (Acked by Eric Anholt)

Signed-off-by: Boyan Ding <boyan.j.ding@gmail.com>
Signed-off-by: Martin Peres <martin.peres@linux.intel.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Emil Velikov <emil.velikov@collabora.co.uk>
diff --git a/configure.ac b/configure.ac
index 9ea9ab2..32fb989 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1568,6 +1568,12 @@
             if test "x$enable_shared_glapi" = xno; then
                 AC_MSG_ERROR([egl_dri2 requires --enable-shared-glapi])
             fi
+            if test "x$enable_dri3" = xyes; then
+                HAVE_EGL_DRIVER_DRI3=1
+                if test "x$enable_shared_glapi" = xno; then
+                    AC_MSG_ERROR([egl_dri3 requires --enable-shared-glapi])
+                fi
+            fi
         else
             # Avoid building an "empty" libEGL. Drop/update this
             # when other backends (haiku?) come along.
@@ -2520,6 +2526,9 @@
     if test "x$HAVE_EGL_DRIVER_DRI2" != "x"; then
         egl_drivers="$egl_drivers builtin:egl_dri2"
     fi
+    if test "x$HAVE_EGL_DRIVER_DRI3" != "x"; then
+        egl_drivers="$egl_drivers builtin:egl_dri3"
+    fi
 
     echo "        EGL drivers:    $egl_drivers"
 fi