print uint64 as uint64.

R=ken
OCL=29568
CL=29570

src/cmd/gc/builtin.c.boot

@@ -8,6 +8,7 @@ char *sysimport =
 	"func sys.printbool (? bool)\n"
 	"func sys.printfloat (? float64)\n"
 	"func sys.printint (? int64)\n"
+	"func sys.printuint (? uint64)\n"
 	"func sys.printstring (? string)\n"
 	"func sys.printpointer (? any)\n"
 	"func sys.printiface (? any)\n"

src/cmd/gc/sys.go

@@ -16,6 +16,7 @@ func	panicl(int32);
 func	printbool(bool);
 func	printfloat(float64);
 func	printint(int64);
+func	printuint(uint64);
 func	printstring(string);
 func	printpointer(any);
 func	printiface(any);

src/cmd/gc/walk.c

@@ -2290,7 +2290,10 @@ loop:
 		on = syslook("printarray", 1);
 		argtype(on, l->type);	// any-1
 	} else if(isint[et]) {
-		on = syslook("printint", 0);
+		if(et == TUINT64)
+			on = syslook("printuint", 0);
+		else
+			on = syslook("printint", 0);
 	} else if(isfloat[et]) {
 		on = syslook("printfloat", 0);
 	} else if(et == TBOOL) {