Fixes #1300. Adding checks for bad CCP transitions and unsettled values

* Now track propagation status and assert on bad statuses
 * Added helper methods to access instruction propagation status
* Modified the phi meet operator to properly reflect the paper it is
based on
* Modified SSA edge addition so that all edge are added, but only on
state changes
* Fixed a bug in instruction simulation where interesting conditional
branches would not mark the interesting edge as executed
 * Added a test to catch this bug
* Added an ostream operator for SSAPropagator::PropStatus