use the debug version of the opengl renderer when built with debug

output/plugins_d.cfg

@@ -6,7 +6,7 @@ PluginFolder=.
 # Define plugins
 # Plugin=RenderSystem_Direct3D9_d
 # Plugin=RenderSystem_Direct3D11
- Plugin=RenderSystem_GL
+ Plugin=RenderSystem_GL_d
 # Plugin=RenderSystem_GLES
 # Plugin=RenderSystem_GLES2
 # Plugin=Plugin_ParticleFX