Fix compatibility problems with newer GLES Khronos headers.

Two sets of problems:

- GLchar was missing from "gl.h".
- GLbyte, GLshort, and GLclampf was in both "gl.h" and "glext.h".

This was fine for building Android, but not for other components that
use more of the Khronos functionality.

Test: Compile Android and other code that needs GLchar, GLbyte, GLshort, and GLclampf.
Change-Id: I47ce0c2a5e985a1088cd8e75a94b3573e4aa7f8e
diff --git a/opengl/include/GLES/gl.h b/opengl/include/GLES/gl.h
index 36acff9..25033f2 100644
--- a/opengl/include/GLES/gl.h
+++ b/opengl/include/GLES/gl.h
@@ -51,6 +51,7 @@
 #ifndef GL_VERSION_ES_CM_1_0
 #define GL_VERSION_ES_CM_1_0 1
 typedef void GLvoid;
+typedef char GLchar;
 typedef unsigned int GLenum;
 #include <KHR/khrplatform.h>
 typedef khronos_float_t GLfloat;