Use canonical suffixes for OCaml programs

Closes #16
Allow us of the optimized compiler toolchain

Closes #18.
Configure available compression tools and prefer xz over bzip2
Add flag for the short functor notation in ocamldoc

The flag ODOC_SHORT_FUNCTORS governs the use of the short functor
notation in ocamldoc.  Its implicit value is yes.

Closes #30.
Merge branches 'topic/16-standard-suffixes-for-program-files', 'topic/18-using-optimised-compilers-toolchain' and 'topic/30-short-functor-notation'