Use GLSLANG_ANGLE to strip features to what ANGLE requires

This change strips a few features similar to GLSLANG_WEB but doesn't
remove every detail like the latter.  It also hardcodes profile/version
to core/450.

In particular, TBuiltIns::initialize is specialized to remove most of
what is not supported or won't be supported by ANGLE.  The result of
this function is parsed with TParseContext::parseShaderStrings which is
a performance bottleneck.

This change shaves about 300KB off of ANGLE's binary size and reduces
the cost of SetupBuiltinSymbolTable to nearly a sixth.

Signed-off-by: Shahbaz Youssefi <ShabbyX@gmail.com>

gtests/Link.FromFile.Vk.cpp

@@ -75,7 +75,7 @@ TEST_P(LinkTestVulkan, FromFile)
     result.linkingOutput = program.getInfoLog();
     result.linkingError = program.getInfoDebugLog();
 
-#ifndef GLSLANG_WEB
+#if !defined(GLSLANG_WEB) && !defined(GLSLANG_ANGLE)
         if (success)
             program.mapIO();
 #endif