GLES2: Clean up entry points for auto-gen.

This cleans up a few things:
 * refactors a few remaining missed EPs
 * removes unnecessary includes
 * rename one Context entry point
 * moves some ES2 EP validation to validationES2

The last item makes for a significant diff, but this is a refactor
change only, with no functionality change.

BUG=angleproject:747

Change-Id: I7860cc4b6260b6c22faa5f2885297333c0cdb4ed
Reviewed-on: https://chromium-review.googlesource.com/483426
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/Context.cpp b/src/libANGLE/Context.cpp
index 58ed24d..28c1fc5 100644
--- a/src/libANGLE/Context.cpp
+++ b/src/libANGLE/Context.cpp
@@ -4240,7 +4240,7 @@
     QueryProgramiv(programObject, pname, params);
 }
 
-void Context::getInfoLog(GLuint program, GLsizei bufsize, GLsizei *length, GLchar *infolog)
+void Context::getProgramInfoLog(GLuint program, GLsizei bufsize, GLsizei *length, GLchar *infolog)
 {
     Program *programObject = getProgram(program);
     ASSERT(programObject);