updated gles20 bindings, fixes broken methods

this adds correct versions of the broken GLES20 methods
glGetShaderSource, glGetActiveAttrib and glGetActiveUniform.
the old functions are still there and need to be @hide later.

Bug: 6006380
Change-Id: I8127a77c4b89aa8a9a54bea88774077535e2139d
3 files changed