New function 'luaL_openselectedlibs'

Makes it easier to start Lua with only some standard libraries.

lua.c

@@ -609,6 +609,10 @@ static void doREPL (lua_State *L) {
 
 /* }================================================================== */
 
+#if !defined(luai_openlibs)
+#define luai_openlibs(L)	luaL_openlibs(L)
+#endif
+
 
 /*
 ** Main body of stand-alone interpreter (to be called in protected mode).
@@ -631,7 +635,7 @@ static int pmain (lua_State *L) {
     lua_pushboolean(L, 1);  /* signal for libraries to ignore env. vars. */
     lua_setfield(L, LUA_REGISTRYINDEX, "LUA_NOENV");
   }
-  luaL_openlibs(L);  /* open standard libraries */
+  luai_openlibs(L);  /* open standard libraries */
   createargtable(L, argv, argc, script);  /* create table 'arg' */
   lua_gc(L, LUA_GCRESTART);  /* start GC... */
   lua_gc(L, LUA_GCGEN, 0, 0);  /* ...in generational mode */