Silence unused-but-set-variable warnings.

core/jni/android_opengl_EGL14.cpp

core/jni/android_opengl_EGL15.cpp

core/jni/android_opengl_EGLExt.cpp

core/jni/android_opengl_GLES10.cpp

core/jni/android_opengl_GLES10Ext.cpp

core/jni/android_opengl_GLES11.cpp

core/jni/android_opengl_GLES11Ext.cpp

core/jni/android_opengl_GLES20.cpp

core/jni/android_opengl_GLES30.cpp

core/jni/android_opengl_GLES31.cpp

core/jni/android_opengl_GLES31Ext.cpp

core/jni/android_opengl_GLES32.cpp

core/jni/com_google_android_gles_jni_GLImpl.cpp

opengl/java/android/opengl/EGLExt.java