Fix typo in _LIBRARY_FEATURE_NAMES.
The missing comma caused the "GL_ES_VERSION_3_1" and "GL_ES_VERSION_3_2" to concatenate into non-existing feature name. Symbols from gles 3.1 and 3.2 were then missing in the generated files.
The missing comma caused the "GL_ES_VERSION_3_1" and "GL_ES_VERSION_3_2" to concatenate into non-existing feature name. Symbols from gles 3.1 and 3.2 were then missing in the generated files.