profiling: Adds initial UProf support across clutter

UProf is a small library that aims to help applications/libraries provide
domain specific reports about performance.  It currently provides high
precision timer primitives (rdtsc on x86) and simple counters, the ability
to link statistics between optional components at runtime and makes report
generation easy.

This adds initial accounting for:
- Total mainloop time
- Painting
- Picking
- Layouting
- Idle time

The timing done by uprof is of wall clock time. It's not based on stochastic
samples we simply sample a counter at the start and end.  When dealing with
the complexities of GPU drivers and with various kinds of IO this form of
profiling can be quite enlightening as it will be able to represent where
your application is blocking unlike tools such as sysprof.

To enable uprof accounting you must configure Clutter with --enable-profile
and have uprof-0.2 installed from git://git.moblin.org/uprof

If you want to see a report of statistics when Clutter applications exit you
should export CLUTTER_PROFILE_OUTPUT_REPORT=1 before running them.

Just a final word of caution; this stuff is new and the manual nature of
adding uprof instrumentation means it is prone to some errors when modifying
code.  This just means that when you question strange results don't rule out
a mistake in the instrumentation.  Obviously though we hope the benfits out
weigh e.g.  by focusing on very key stats and by having automatic reporting.

clutter/clutter-backend.c

@@ -46,6 +46,7 @@
 #include "clutter-fixed.h"
 #include "clutter-marshal.h"
 #include "clutter-private.h"
+#include "clutter-profile.h"
 
 #include <cogl/cogl.h>
 
@@ -302,10 +303,24 @@ _clutter_backend_redraw (ClutterBackend *backend,
                          ClutterStage   *stage)
 {
   ClutterBackendClass *klass;
+  CLUTTER_STATIC_COUNTER (redraw_counter,
+                          "_clutter_backend_redraw counter",
+                          "Increments for each _clutter_backend_redraw call",
+                          0 /* no application private data */);
+  CLUTTER_STATIC_TIMER (redraw_timer,
+                        "Mainloop", /* parent */
+                        "Redrawing",
+                        "The time spent redrawing everything",
+                        0 /* no application private data */);
+
+  CLUTTER_COUNTER_INC (_clutter_uprof_context, redraw_counter);
+  CLUTTER_TIMER_START (_clutter_uprof_context, redraw_timer);
 
   klass = CLUTTER_BACKEND_GET_CLASS (backend);
   if (G_LIKELY (klass->redraw))
     klass->redraw (backend, stage);
+
+  CLUTTER_TIMER_STOP (_clutter_uprof_context, redraw_timer);
 }
 
 gboolean