Fix luac errorformat
Fix luac errorformat

Newer versions of luac prepend error messages with the actual name of
the executable.

Reference: http://www.lua.org/source/5.3/luac.c.html#fatal

Picked from Syntastic: https://github.com/scrooloose/syntastic/commit/90b19d1.

bonds/neomake,bonds/neomake,datanoise/neomake,nerdrew/neomake,neomake/neomake,codeinabox/neomake,euclio/neomake,euclio/neomake,nerdrew/neomake,neomake/neomake