Replace _mesa_malloc, _mesa_calloc and _mesa_free with plain libc versions

src/mesa/drivers/x11/xm_buffer.c

@@ -242,7 +242,7 @@ xmesa_delete_renderbuffer(struct gl_renderbuffer *rb)
     * should probably get freed here, but that's currently done in
     * XMesaDestroyBuffer().
     */
-   _mesa_free(rb);
+   free(rb);
 }
 
 
@@ -412,11 +412,11 @@ xmesa_delete_framebuffer(struct gl_framebuffer *fb)
    }
 
    if (b->rowimage) {
-      _mesa_free( b->rowimage->data );
+      free( b->rowimage->data );
       b->rowimage->data = NULL;
       XMesaDestroyImage( b->rowimage );
    }
 
    _mesa_free_framebuffer_data(fb);
-   _mesa_free(fb);
+   free(fb);
 }