String buffers, part 2d: basic string buffer methods.

Sponsored by fmad.io.

src/lj_lib.h

@@ -46,6 +46,12 @@ LJ_FUNC GCtab *lj_lib_checktab(lua_State *L, int narg);
 LJ_FUNC GCtab *lj_lib_checktabornil(lua_State *L, int narg);
 LJ_FUNC int lj_lib_checkopt(lua_State *L, int narg, int def, const char *lst);
 
+#if LJ_HASBUFFER
+LJ_FUNC GCstr *lj_lib_checkstrx(lua_State *L, int narg);
+LJ_FUNC int32_t lj_lib_checkintrange(lua_State *L, int narg,
+				     int32_t a, int32_t b);
+#endif
+
 /* Avoid including lj_frame.h. */
 #if LJ_GC64
 #define lj_lib_upvalue(L, n) \