Speed up elaboration of larger functions

Mostly by making atH less stupid when searching for a hole (there is
more needs to be done on this...)
Merge branch 'master' of github.com:edwinb/Idris-dev
Reorder goal search for efficiency

Better to search first in places where the goal is most likely to be!
Another minor efficiency gain in elaborator

Call updateSolved less often. Also cut down search in Effects to depth
of 20 (this still needs to be done better, but it seems to have a large
effect on typechecking time for effects programs).
Allow eof instead of eol for comments