Add some tests for redeclarations of builtins

Add some tests for redeclarations of builtins

From Section 3.7. (Identifiers) of the GLSL 4.60 spec:

   "Identifiers starting with “gl_” are reserved for use by OpenGL,
   and in general, may not be declared in a shader; this results in
   a compile-time error. However, as noted in the specification,
   there are some cases where previously declared variables can be
   redeclared, and predeclared “gl_” names are allowed to be
   redeclared in a shader only for these specific purposes."

The specific cases where redeclaration is allowed are cases where
invariant is added, precision qualifiers are added, an array size is
added, etc.

Components: OpenGL
Affects: KHR-GL[34]*.shaders30.declarations.declarations*

Change-Id: Ifa39311d64e24d8e1a419959a2e6b2252991e694