runtime: In backtraces, get inline functions, skip split-stack fns.

R=iant
CC=gofrontend-dev
https://golang.org/cl/7221076
diff --git a/libgo/runtime/go-caller.c b/libgo/runtime/go-caller.c
index 63b45f3..d84580f 100644
--- a/libgo/runtime/go-caller.c
+++ b/libgo/runtime/go-caller.c
@@ -166,16 +166,16 @@
 Caller (int skip)
 {
   struct caller_ret ret;
-  uintptr pc;
+  Location loc;
   int32 n;
-  String fn;
 
   runtime_memclr (&ret, sizeof ret);
-  n = runtime_callers (skip + 1, &pc, 1);
+  n = runtime_callers (skip + 1, &loc, 1);
   if (n < 1)
     return ret;
-  ret.pc = pc;
-  __go_file_line (pc, &fn, &ret.file, &ret.line);
+  ret.pc = loc.pc;
+  ret.file = loc.filename;
+  ret.line = loc.lineno;
   ret.ok = 1;
   return ret;
 }