Proposition to improve build portability

Here are some changes I've done a little while ago to be able to use ctrlp-cmatcher on my systems (mainly some *BSD).
I'm saying "improve" but this might be subjective and will depend on what platforms are considered to be officially supported.

Let me know any change needed so it could be accepted in a way or another, my principal need would be to be able to use ctrlp-cmatcher easily, without the requirements to build/install bash on many boxes, and this only for one vim plugin even if I really like a lot ctrlp-cmatcher matching behavior ;-)