check_bounds: traverse call-graph to propagate information at a call-site (#425)

* move pre_schedule_checks to be translation-unit-wide

* export linearize from loopy module

* check_bounds: traverse the call graph to include constraints from passed value-args

* adds test: test_check_bounds_with_caller_assumptions

* gets rid of spurious newlines

Co-authored-by: Andreas Kloeckner <inform@tiker.net>

* adds a fixme to take caller's iname domains into account

Co-authored-by: Andreas Kloeckner <inform@tiker.net>