(PUP-1576) Make hyphen in bare words legal (future parser)

This adds the ability to use a hyphen in a bare word. The result is the
same as if the bare word had been quoted in single quotes. It is not
allowed to start or end a bare word with a hyphen, those are always
interpreted as :MINUS.
Merge pull request #2393 from hlindberg/pup-1576_allow-hyphen-in-bare-words

(PUP-1576) Make hyphen in bare words legal (future parser)