Make it easier to disable tracing

TRAC #11979

Signed-off-by: Shannon Woods
Signed-off-by: Daniel Koch

Author:    Andrew Lewycky

git-svn-id: https://angleproject.googlecode.com/svn/trunk@178 736b8ea6-26fd-11df-bfd4-992fa37f6226

src/common/debug.cpp

@@ -11,11 +11,13 @@
 #include <stdio.h>
 #include <stdarg.h>
 
+static bool trace_on = true;
+
 namespace gl
 {
 void trace(const char *format, ...)
 {
-    if (true)
+    if (trace_on)
     {
         if (format)
         {