Add glCompressedTexImage2D to glplatform header.
Add glCompressedTexImage2D to glplatform header.

Fix for the Windows build.

Tested on Windows and Linux.

Change-Id: I2d92eb6387e4cc161a9004f6e22c3f770559e96f

google/fplbase,google/fplbase,google/fplbase,google/fplbase