Merge: phases: do not reanalyze amodules in run_phase

Multiple `run_phase` invocation should not analyze a amodule twice.

This is a workaround, the whole phase API should be improved to make late
module loading less error-prone and more simple.

Close #726

Pull-Request: #729
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>

diff --cc src/phase.nit
Simple merge