state_tracker: replace __FUNCTION__ with __func__

Consistently just use C99's __func__ everywhere.
The patch was verified with Microsoft Visual studio 2013
redistributable package(RTM version number: 18.0.21005.1)
Next MSVC versions intends to support __func__.
No functional changes.

Acked-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Marius Predut <marius.predut@intel.com>

src/mesa/state_tracker/st_atom_constbuf.c

@@ -92,7 +92,7 @@ void st_upload_constants( struct st_context *st,
 
       if (ST_DEBUG & DEBUG_CONSTANTS) {
          debug_printf("%s(shader=%d, numParams=%d, stateFlags=0x%x)\n",
-                      __FUNCTION__, shader_type, params->NumParameters,
+                      __func__, shader_type, params->NumParameters,
                       params->StateFlags);
          _mesa_print_parameter_list(params);
       }