runtime: move gosched to Go, to add stack frame information

LGTM=khr
R=khr
CC=golang-codereviews
https://golang.org/cl/134520044

src/runtime/malloc.go

@@ -477,7 +477,7 @@ func gogc(force int32) {
 	// now that gc is done, kick off finalizer thread if needed
 	if !concurrentSweep {
 		// give the queued finalizers, if any, a chance to run
-		gosched()
+		Gosched()
 	}
 }
 

src/runtime/mgc0.go

@@ -89,7 +89,7 @@ func bgsweep() {
 	for {
 		for gosweepone() != ^uintptr(0) {
 			sweep.nbgsweep++
-			gosched()
+			Gosched()
 		}
 		lock(&gclock)
 		if !gosweepdone() {

src/runtime/proc.c

@@ -1677,18 +1677,7 @@ runtime·park_m(G *gp)
 	schedule();
 }
 
-// Scheduler yield.
-#pragma textflag NOSPLIT
-void
-runtime·gosched(void)
-{
-	void (*fn)(G*);
-	
-	fn = runtime·gosched_m;
-	runtime·mcall(&fn);
-}
-
-// runtime·gosched continuation on g0.
+// Gosched continuation on g0.
 void
 runtime·gosched_m(G *gp)
 {

src/runtime/runtime.h

@@ -852,7 +852,6 @@ void	runtime·setg(G*);
 void	runtime·newextram(void);
 void	runtime·exit(int32);
 void	runtime·breakpoint(void);
-void	runtime·gosched(void);
 void	runtime·gosched_m(G*);
 void	runtime·schedtrace(bool);
 void	runtime·park(bool(*)(G*, void*), void*, String);

src/runtime/stubs.go

@@ -130,7 +130,6 @@ func memclr(ptr unsafe.Pointer, n uintptr)
 //go:noescape
 func memmove(to unsafe.Pointer, from unsafe.Pointer, n uintptr)
 
-func gosched()
 func starttheworld()
 func stoptheworld()
 func newextram()