String buffers, part 2a: internal SBuf reorg. Use full pointers.

Sponsored by fmad.io.

src/lj_profile.c

@@ -346,8 +346,7 @@ LUA_API void luaJIT_profile_stop(lua_State *L)
     lj_trace_flushall(L);
 #endif
     lj_buf_free(g, &ps->sb);
-    setmref(ps->sb.b, NULL);
-    setmref(ps->sb.e, NULL);
+    ps->sb.w = ps->sb.e = NULL;
     ps->g = NULL;
   }
 }
@@ -362,7 +361,7 @@ LUA_API const char *luaJIT_profile_dumpstack(lua_State *L, const char *fmt,
   lj_buf_reset(sb);
   lj_debug_dumpstack(L, sb, fmt, depth);
   *len = (size_t)sbuflen(sb);
-  return sbufB(sb);
+  return sb->b;
 }
 
 #endif