runtime: update out-of-date comment

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5532118

src/pkg/runtime/asm_arm.s

@@ -277,7 +277,7 @@ TEXT runtime·abort(SB),7,$-4
 //	}else
 //		return 0;
 //
-// To implement runtime·cas in ../$GOOS/arm/sys.s
+// To implement runtime·cas in sys_$GOOS_arm.s
 // using the native instructions, use:
 //
 //	TEXT runtime·cas(SB),7,$0

src/pkg/runtime/cgocall.c

@@ -17,7 +17,7 @@
 // so as not to block other goroutines or the garbage collector,
 // and then calls runtime.asmcgocall(_cgo_Cfunc_f, frame). 
 //
-// runtime.asmcgocall (in $GOARCH/asm.s) switches to the m->g0 stack
+// runtime.asmcgocall (in asm_$GOARCH.s) switches to the m->g0 stack
 // (assumed to be an operating system-allocated stack, so safe to run
 // gcc-compiled code on) and calls _cgo_Cfunc_f(frame).
 //
@@ -55,7 +55,7 @@
 // with 6c instead of gcc, can refer to dotted names like
 // runtime.cgocallback and p.GoF.)
 //
-// runtime.cgocallback (in $GOOS/asm.s) switches from m->g0's
+// runtime.cgocallback (in asm_$GOARCH.s) switches from m->g0's
 // stack to the original g (m->curg)'s stack, on which it calls
 // runtime.cgocallbackg(p.GoF, frame, framesize).
 // As part of the stack switch, runtime.cgocallback saves the current

src/pkg/runtime/sys_freebsd_386.s

@@ -238,7 +238,7 @@ int i386_set_ldt(int, const union ldt_entry *, int);
 // setldt(int entry, int address, int limit)
 TEXT runtime·setldt(SB),7,$32
 	MOVL	address+4(FP), BX	// aka base
-	// see comment in linux/386/sys.s; freebsd is similar
+	// see comment in sys_linux_386.s; freebsd is similar
 	ADDL	$0x8, BX
 
 	// set up data_desc

src/pkg/runtime/thread_darwin.c

@@ -39,7 +39,7 @@ runtime·semacreate(void)
 void
 runtime·osinit(void)
 {
-	// Register our thread-creation callback (see {amd64,386}/sys.s)
+	// Register our thread-creation callback (see sys_darwin_{amd64,386}.s)
 	// but only if we're not using cgo.  If we are using cgo we need
 	// to let the C pthread libary install its own thread-creation callback.
 	if(!runtime·iscgo)
@@ -338,7 +338,7 @@ runtime·mach_semdestroy(uint32 sem)
 	}
 }
 
-// The other calls have simple system call traps in sys.s
+// The other calls have simple system call traps in sys_darwin_{amd64,386}.s
 int32 runtime·mach_semaphore_wait(uint32 sema);
 int32 runtime·mach_semaphore_timedwait(uint32 sema, uint32 sec, uint32 nsec);
 int32 runtime·mach_semaphore_signal(uint32 sema);