Move to a shared lib model for

Move to a shared lib model for
1) checkers (one lib for all checkers for a start)
2) prioritizers (one helper lib, plus one lib per prioritizer)
3) libmultipath

Collaterals include :
o Remove old prioritizer callouts.
o Drop the klibc support
o Add remove_map(s)/remove_map(s)_and_stop_waiter(s) helpers

Regression testing is needed now.