mesa: remove unneeded glthread.c file

The _glthread_GetID() function is also defined in mapi_glapi.c

Reviewed-by: José Fonseca <jfonseca@vmware.com>

src/mapi/glapi/Makefile.sources

@@ -6,7 +6,6 @@ GLAPI_SOURCES = \
 	glapi_gentable.c \
 	glapi_getproc.c \
 	glapi_nop.c \
-	glthread.c \
 	glapi.c
 
 X86_API =			\

src/mapi/glapi/SConscript

@@ -34,7 +34,6 @@ glapi_sources = [
     'glapi_entrypoint.c',
     'glapi_getproc.c',
     'glapi_nop.c',
-    'glthread.c',
     'glapi.c',
 ]
 

src/mapi/glapi/glthread.c

@@ -1,7 +0,0 @@
-#include "glapi/glapi.h"
-
-unsigned long
-_glthread_GetID(void)
-{
-   return u_thread_self();
-}