tweak lua gc

lua C++ bindings require ~400KB worth of tables now; so bump memory
available to rt-safe scripts (full interpreter) to 2MB.

Also switch to incremental GC.

libs/lua/lua/luastate.h

@@ -34,6 +34,8 @@ public:
 	int do_command (std::string);
 	int do_file (std::string);
 	void collect_garbage ();
+	void collect_garbage_step ();
+	void tweak_rt_gc ();
 
 	sigc::signal<void,std::string> Print;
 

libs/lua/luastate.cc

@@ -76,6 +76,17 @@ LuaState::collect_garbage () {
 	lua_gc (L, LUA_GCCOLLECT, 0);
 }
 
+void
+LuaState::collect_garbage_step () {
+	lua_gc (L, LUA_GCSTEP, 0);
+}
+
+void
+LuaState::tweak_rt_gc () {
+	//lua_gc (L, LUA_GCSETPAUSE, 20);
+	lua_gc (L, LUA_GCSETSTEPMUL, 100);
+}
+
 void
 LuaState::print (std::string text) {
 	Print (text); /* EMIT SIGNAL */