ES31: Add PROGRAM_SEPARABLE to ProgramParameter and GetProgram

BUG=angleproject:1939
TEST=angle_end2end_tests

Change-Id: I97ad11360f7c015947a2c0cc7d4a47f994726834
Reviewed-on: https://chromium-review.googlesource.com/454264
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/ProgramVk.cpp b/src/libANGLE/renderer/vulkan/ProgramVk.cpp
index d9767da..b0a06dd 100644
--- a/src/libANGLE/renderer/vulkan/ProgramVk.cpp
+++ b/src/libANGLE/renderer/vulkan/ProgramVk.cpp
@@ -53,6 +53,11 @@
     UNIMPLEMENTED();
 }
 
+void ProgramVk::setSeparable(bool separable)
+{
+    UNIMPLEMENTED();
+}
+
 LinkResult ProgramVk::link(ContextImpl *contextImpl,
                            const gl::VaryingPacking &packing,
                            gl::InfoLog &infoLog)