Macros beginning with GL_* are reserved by GLSL.

Fixing code to not use reserved keywords. From GLSL 4.3 spec (page 11):

  All macro names containing two consecutive underscores ( __ ) are reserved for
  future use as predefined macro names. All macro names prefixed with “GL_”
  (“GL” followed by a single underscore) are also reserved.

Change-Id: I6e0fa27385b1aaef50b18a383f381224100e673d
Merge topic 'fix_reserved_words' into master

fb1f4dd7 Macros beginning with GL_* are reserved by GLSL.