[ refactor ] packed up results of checkLeftHandSide in a datatype

This is in preparation for proper postponing of lhs checking. Still a lot
of work to be done though.
[ test ] test case for postponing lhs (disabled at the moment)
Merge branch 'maint-2.4.0' from github
[ issue1130 ] fixed

Copy pasted telescope reordering from with-abstraction. Would have
been nice to reuse the code, but refactoring the with-checker is
non-trivial.
[ issue1130 ] updated test case