old-build: define a new symbol

waf has a proper test, but no test was added to old-configure.

This means that on OSX, old-configure is not supposed to work anymore.
But still allow it to compile cleanly on OSX.
player: reorganize how lua scripts are loaded

Make loading of scripts independent of Lua. Move some of the loading
code from lua.c to scripting.c, and make it easier to add new scripting
backends.