Advertise GL_ANGLE_texture_usage.

src/libGLESv2/Context.cpp

@@ -3445,6 +3445,8 @@ void Context::initExtensionString()
     {
         mExtensionString += "GL_ANGLE_texture_compression_dxt5 ";
     }
+
+    mExtensionString += "GL_ANGLE_texture_usage ";
     mExtensionString += "GL_ANGLE_translated_shader_source ";
 
     // Other vendor-specific extensions