Everything that needs the lua_State should create a local variable like this:
lua_State *L = globalconf_get_lua_State();
This ensures that the compiler warns if there are two variables with name "L" in
scope. The idea here is that it should become harder to accidentally use the
global lua state instead of the state of the current state.
While writing this commit, I found another place that gets its wrong: Reading
client.focus from a coroutine was broken, since it was returning the result on
the main thread instead of the current one.
Signed-off-by: Uli Schlachter <psychon@znc.in>