I thought this would be an easy one but what do I need to include
Huh, that's very optimistic opinion for something such complex as Newsie :)
to get the GEM objects SELECTABLE, TOUCHEXIT etc. ?
Generally, gemlib (libgem) package. But be prepared not all variables have same names... so you need some knowledge of GEM programming, to be sure you don't exchange some bits / flags.
gcc throws up loads of warnings and errors in the code, it's amazing.
That means the code is most probably very badly written.