glPushDebugGroup & glPopDebugGroup and unavailable function warnings

When replaying my traces for code that uses glPushDebugGroup and glPopDebugGroup cause warnings to be displayed (as my host GL implementation doesn't support them).

warning: ignoring call to unavailable function glPushDebugGroup
warning: ignoring call to unavailable function glPopDebugGroup
warning: ignoring call to unavailable function glPushDebugGroup
warning: ignoring call to unavailable function glPopDebugGroup

For any descent size trace this will cause the "error" log in the qapitrace tool to slow to a crawl after I generate thumnails. ( or in general replay the trace).  

This patch adds the ability to disable the warning messages for certain GL calls