Included targets in cabal's bash-completion.

When commpleting for cabal build/repl/test/bench, this completes the possible
targets depending on their types.  This is a temporary workaround, the
definitive solution would be to include those targets in cabal itself, via
``--list-options''.
Merge branch 'master' of github.com:haskell/cabal
cabal's bash-cmpl: handling execs and improvements

Now handling executables:
	- completing run target
	- completing executables on build target

Improvements:
	- removed false positives on completion
Merge pull request #1932 from rudymatela/master

Included targets in cabal's bash-completion.