Define glibtop_debug(_r) as macros, eventually calling real C function.

Keep these as macros so that if debug is not enable, although the
debug message is parsed, it's not run.
It's better this way because the debug message is always parsed and
checked instead of being deleted by the preprocessor.

sysdeps/common/error.c

@@ -174,7 +174,7 @@ glibtop_debug_vr (glibtop *server, const char *format, va_list args)
 }
 
 void
-glibtop_debug_r (glibtop *server, const char *format, ...)
+glibtop_debug_r_real (glibtop *server, const char *format, ...)
 {
 	va_list args;