Only enable verbose NoOp dispatch if DEBUG is defined

Only enable verbose NoOp dispatch if DEBUG is defined

By default we generate a function per GL entry point to warn if it's
called without a context set.  This is to allow the function to print
it's name in the warning.  By using a generic function that doesn't print
the function name in the non-DEBUG case, we reduce libGL size from
320008 bytes to 283144 bytes (11%).