loadlua() simplification

loadlua() simplification

nhl_loadlua() went from too simple to too complicated, now somewhere
in between.  Still doesn't assume that an entire file can be scooped
up with a single fread(), but no longer mucks about with the contents
of the file in order to insert a comment containing the file's name.
In order to have useful filename feedback in Lua error messages, just
use a different liblua routine to feed the file's contents to it.