[PATCH 00 of 11 c-hglib:level0 V2] c-hglib API level 0

[Iulian Stana]

This is a draft of my work for c-hglib up to now, I am sending this to the list
for public review (even if this is not a patch for the core mercurial). I am
sure that the main developers following my work (Matt, Pierre-Yves, Idan and
others) will have important remarks on the architecture and on the style, and I
like to solicit those feedbacks.
I know that I already send this work before, but I would like to send it again
in a more detailed way. I would like to know that everything is clear and works
how it should.