Add low-overhead profiler. Part 1: interpreter, low-level C API.

src/luajit.h

@@ -64,6 +64,15 @@ enum {
 /* Control the JIT engine. */
 LUA_API int luaJIT_setmode(lua_State *L, int idx, int mode);
 
+/* Low-overhead profiling API. */
+typedef void (*luaJIT_profile_callback)(void *data, lua_State *L,
+					int samples, int vmstate);
+LUA_API void luaJIT_profile_start(lua_State *L, const char *mode,
+				  luaJIT_profile_callback cb, void *data);
+LUA_API void luaJIT_profile_stop(lua_State *L);
+LUA_API const char *luaJIT_profile_dumpstack(lua_State *L, const char *fmt,
+					     int depth, size_t *len);
+
 /* Enforce (dynamic) linker error for version mismatches. Call from main. */
 LUA_API void LUAJIT_VERSION_SYM(void);