Add netloc

Library source files go under netloc/* on the side of hwloc/
Headers, tests, utils are added near hwloc ones.

doc/main.doxy is added, which includes the former hwloc.doxy and the new netloc.doxy
To be better integrated later.
jansson: remove -Wdeclaration-after-statement from AM_CFLAGS

It doesn't work with all versions of gcc, so just take it out.
jansson: bring the upstream fix for GNU-specific make-ism

Bring
  https://github.com/akheron/jansson/issues/203
and disable the configure code so that we don't pollute AM_CFLAGS everywhere.
jansson Makefile.am: remove use of -version-info

-version-info is ignored for Libtool convenience libraries (and
Libtool warns about it).  So just remove it.
netloc_gather_ib: fix the parsing of IB port state

Thanks to Chih-Song Kuo for reporting the issue.
doc: document that lstopo should be used with cgroup/cpuset

Suggested by Chih-Song Kuo
doxy: integrate hwloc.doxy and netloc.doxy through a main.doxy

Add a global introduction, and the common install instructions
and strip things from hwloc and netloc sections.
Add references in all directions to ease things.

One thing that remains to be updated/merged is the bug report section,
we'll fix this later once the actual merge is done and once we know
where netloc bug reports should be sent.