Just to be on the safe side about avoiding other portability hazards

Just to be on the safe side about avoiding other portability hazards
in future, add `-ansi -pedantic' to the Halibut default compile
options and fix the few resulting warnings (mostly signed/unsigned
char mismatches and commas at the ends of enums). The one remaining
warning I'm still seeing is `missing initializer' for the big table
in charset/iso2022.c, but I think the code genuinely is more
readable this way, and I haven't found a gcc option to disable that
specific warning.

git-svn-id: svn://svn.tartarus.org/sgt/halibut@6458 cda61777-01e9-0310-a592-d414129be87e