[PATCH 0 of 5 V3 c-hglib] Examples for Level 0 functions, leftover GSoC 2013

[Giovanni Gherdovich]

Please note that this series is not for the hg repo,
but for the c-hglib project (C bindings for hg),
which lives at https://bitbucket.org/mpmselenic/c-hglib

This series is V3 with respect to 

http://markmail.org/message/ux5jvhgz7p4jri4l and
http://markmail.org/message/dzgdp5acax7h26de

After this patch will be reviewed, upcoming patches are:

* a Makefile (already prepared, see https://bitbucket.org/gghh/c-hglib/commits/3450b2bacd1bc27126dcfab980463051f2057447 )
* a mini-framework for unit tests in C (based on assert(3)), in the making
* tests for level 0 functions.

I know Mercurial doesn't do unit tests,
http://www.selenic.com/blog/?p=582 , but as I understand mpm's post
the point is that you can't unit-test a moving target as
mercurial internal API is; OTOH c-hglib is meant to be a stable API
and so unit tests make sense.

Later, we'll tackle the integration of the monster 55-patch series,
namely level 1 functions (aka command-level API):
http://markmail.org/thread/vrq243asw6tdep3c