Add support for ES31 context creation

The dEQP test for context creation passes.

SH_WEBGL3_SPEC has been added, but it should be considered whether we
should keep it, remove it or rename it. It was added so that there is
a webgl mapping to es 310 shaders. Check Compiler.cpp. The bison file
has been modified so that some tokens from es3 can be also used in
es31 as well.

A separate macro ES3_1_ONLY is added so that some tokens are limited
only for es 310 shaders.

BUG=angleproject:1442
TEST=angle_unittests

Change-Id: I2e5ca227c96046c30dc796ab934f3fda9c533eba
Reviewed-on: https://chromium-review.googlesource.com/360300
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/tests/gl_tests/TextureTest.cpp b/src/tests/gl_tests/TextureTest.cpp
index b36593b..1242e03 100644
--- a/src/tests/gl_tests/TextureTest.cpp
+++ b/src/tests/gl_tests/TextureTest.cpp
@@ -188,7 +188,7 @@
 
         setUpProgram();
 
-        if (getClientVersion() < 3)
+        if (getClientMajorVersion() < 3)
         {
             if (!extensionEnabled("GL_OES_texture_float"))
             {