doc: update information in the Installation Manual

doc: update information in the Installation Manual

- update the list of supported platforms according to current known status;

- updated URL links to all dependencies to the current known URL;

- moved the dependency on Autotools to a dedicated section, because it is
not supposed to be necessary for people compiling from the distributed
source archive, and updated the version according to current status;

- extended the chapter on getting the sources to contain all info that
could be needed;

- added a note about compiler requirement to ease understanding the actual
requirements;

- documented some long-time known dependancies (libbsd, inotify, boehm gc);

- fixed a few strings here and there;

- made an appropriate reference to the README.i18n for the troubleshooting
of NLS.

Signed-off-by: Christophe CURIS <christophe.curis@free.fr>