runtime: print PC, not the counter, for a cgo traceback

Change-Id: I54ed7a26a753afb2d6a72080e1f50ce9fba7c183
Reviewed-on: https://go-review.googlesource.com/23228
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/traceback.go

@@ -1039,7 +1039,7 @@ func printOneCgoTraceback(pc uintptr, max int, arg *cgoSymbolizerArg) int {
 		if arg.file != nil {
 			print(gostringnocopy(arg.file), ":", arg.lineno, " ")
 		}
-		print("pc=", hex(c), "\n")
+		print("pc=", hex(pc), "\n")
 		c++
 		if arg.more == 0 {
 			break