update emacs support for GHC 7.6
fix search for hsenv directories
use appropriate option names for older GHC versions
tidy up directory search; remove trailing whitespace
use absolute paths in directory search
support several package-dbs
hsenv.el Strip trailing whitespace
Emacs hsenv mode updates for GHC 7.6 compatibility, with new support for multiple package databases

Merge branch 'emacs_update'
Depend on cl package for mapcar*, block and return.