mesa: separate exec allocation from initialization

In glapi/gl_genexec.py:
* Remove _mesa_alloc_dispatch_table call

In glapi/gl_genexec.py and api_exec.h:
* Rename _mesa_create_exec_table to _mesa_initialize_exec_table

In context.c:
* Call _mesa_alloc_dispatch_table instead of _mesa_create_exec_table
* Call _mesa_initialize_exec_table (this is temporary)

Once all drivers have been modified to call
_mesa_initialize_exec_table, then the call to
_mesa_initialize_context can be removed from context.c.

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/mesa/main/context.c

@@ -935,8 +935,11 @@ _mesa_initialize_context(struct gl_context *ctx,
       return GL_FALSE;
    }
 
-   /* setup the API dispatch tables */
-   ctx->Exec = _mesa_create_exec_table(ctx);
+   /* setup the API dispatch tables with all nop functions */
+   ctx->Exec = _mesa_alloc_dispatch_table(_gloffset_COUNT);
+
+   /* setup the API exec functions */
+   _mesa_initialize_exec_table(ctx);
 
    if (!ctx->Exec) {
       _mesa_reference_shared_state(ctx, &ctx->Shared, NULL);