[syslinux] Chain module - chaindev branch

[Michal Soltys]

git://git.hasevolq.net/syslinux.git

Split and expanded version of chain module is on the chaindev branch.
The module is fully documented in doc/chain.txt

I wasn't sure if to make one giant commit, or kept all the history as I 
was going - so I chose the latter. Tag 'chaindev-review' marks the commit.

New feats since my last mail include options: mbrchs, hideall, bss, bs, 
warn (see doc/chain.txt for details). setbpb is a composite option now, 
adjusting fields basing on bpb detection. Lots of other misc changes and 
a few bugfixes.

Branch disklib contains small patch I sent a few days ago.