Write man pages for public API

[Didier Barvaux]

It would be great to have some nice man pages for every function of the public API and also a global one that describes the library.

Some inputs for writing man pages: http://en.wikipedia.org/wiki/Man_page#Writing_man_pages
Doxygen (already used to generate HTML doc) may eventually be used to generate man pages.

[Didier Barvaux (didier-barvaux)]

help2man could be a great tool for apps/tools.

[Didier Barvaux (didier-barvaux)]

Three kinds of man pages added:
   - static general man pages: rohc(7), rohc_protocol(7), and rohc_library(7),
   - generated man pages for public headers and functions,
   - generated man pages for tools from the app/ subdir.

The generated man pages for public headers and functions are created from doxygen's XML output by the doxy2man tool from https://github.com/gsauthof/doxy2man . The tool was modified to handle groups, typedef, enums, function prototypes, warnings, examples...

Add new kind of man pages: pages for tools of the app/ subdir. They are generated from the output of their --version and --help options by the application help2man.

See http://bazaar.launchpad.net/~didier-barvaux/rohc/main/revision/866 and http://bazaar.launchpad.net/~didier-barvaux/rohc/main/revision/867