runtime: add memory profiling, disabled.
no way to get the data out yet.

add prototype for runtime.Callers,
missing from last CL.

R=r
CC=golang-dev
https://golang.org/cl/713041
diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index 622f680..c046938 100644
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -359,7 +359,8 @@
 void	mcpy(byte*, byte*, uint32);
 int32	mcmp(byte*, byte*, uint32);
 void	memmove(void*, void*, uint32);
-void*	mal(uint32);
+void*	mal(uintptr);
+void*	malx(uintptr size, int32 skip_delta);
 uint32	cmpstring(String, String);
 String	gostring(byte*);
 String	gostringw(uint16*);