Omit fromList in Show/Read instances

Fixes #14.
Fix missing haddocks for `overlaps` and `basicOverlaps`
Merge pull request #17 from nh2/overlap-haddocks

Fix missing haddocks for `overlaps` and `basicOverlaps`
Make all cabal flags manual

This means that dependency solver's job is easier (it doesn't need to
consider the opposite flag setting) and it means that cabal cannot
automatically switch these flags (which I don't think happened in the
past, but it's theoretically possible).
Move CPP pragmas outside {-# RULES #-}, re #21.