2 fixes:

* Move the commit block forwards after writing a checked, disabled invoke instruction.
* Reinstate accidentally disabled commit-disabled-allocations path.

Also add a utility function for finding basic blocks by name from gdb.
Fix: invoke instructions with IAs but not committed may require a check, in which case branch to the check subblock rather than the natural successor.
Fix silly misplaced predicate in identifying breaks to top-of-block from failing invokes.
Yet another missing piece: fill in PHI members correctly when a failed invoke branches to the top of a block.
Fix the rare case where a check for a failed load or call converges with a check for a failed VFS call, which is possible since the former skips backwards one instruction.
When checking a real value against a multi-val it is supposed to match, make sure to convert pointer typed values to integers first.