Add a mechanism for determining GPU driver details

This adds a CoglGpuInfo struct to the CoglContext which contains some
enums describing the GL driver in use. This currently includes the
driver package (ie, is it Mesa) the version number of the package and
the vendor of the GPU (ie, is it by Intel). There is also a bitmask
which will contain the workarounds that we should do for that
particular driver configuration. The struct is initialised on context
creation by using a series of string comparisons on the strings
returned from glGetString.

Reviewed-by: Robert Bragg <robert@linux.intel.com>

cogl/cogl-context-private.h

@@ -48,6 +48,7 @@
 #include "cogl-texture-3d.h"
 #include "cogl-texture-rectangle.h"
 #include "cogl-sampler-cache-private.h"
+#include "cogl-gpu-info-private.h"
 
 typedef struct
 {
@@ -64,6 +65,10 @@ struct _CoglContext
 
   CoglDriver driver;
 
+  /* Information about the GPU and driver which we can use to
+     determine certain workarounds */
+  CoglGpuInfo gpu;
+
   /* vtables for the driver functions */
   const CoglDriverVtable *driver_vtable;
   const CoglTextureDriver *texture_driver;