re PR go/69511 (G.gcstack_size uses uintptr instead of size_t)

	PR go/69511
    runtime: change G gcstack_size field to size_t
    
    Because its address is passed to __splitstack_find, which expects size_t*.
    
    From Dominik Vogt in GCC PR 69511.
    
    Reviewed-on: https://go-review.googlesource.com/19429

From-SVN: r233260

gcc/go/gofrontend/MERGE

-2ef5f1ca449b5cf07dbbd7b13a50910fb5567372
+4cec4c5db5b054c5536ec5c50ee7aebec83563bc
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/runtime/proc.c

@@ -2267,7 +2267,7 @@ runtime_malg(int32 stacksize, byte** ret_stack, size_t* ret_stacksize)
 		}
 		*ret_stacksize = stacksize;
 		newg->gcinitial_sp = *ret_stack;
-		newg->gcstack_size = stacksize;
+		newg->gcstack_size = (size_t)stacksize;
 #endif
 	}
 	return newg;

libgo/runtime/runtime.h

@@ -200,7 +200,7 @@ struct	G
 	void*	exception;	// current exception being thrown
 	bool	is_foreign;	// whether current exception from other language
 	void	*gcstack;	// if status==Gsyscall, gcstack = stackbase to use during gc
-	uintptr	gcstack_size;
+	size_t	gcstack_size;
 	void*	gcnext_segment;
 	void*	gcnext_sp;
 	void*	gcinitial_sp;