build-sys: use automake subdir-object
build-sys: remove unnecessary files
docs: update Doxyfile

Just a simple 'doxygen -u' version update.
build-sys: include config.h to all files using automake

Do not try to be too smart which compilations need config.h, as most of
them will simply because of the config.h has information about system
capabilities.
build-sys: use AC_USE_SYSTEM_EXTENSIONS

The earlier _GNU_SOURCE definitions possibly did not take effect
everywhere where it was intended.
build-sys: move autotools files to subdirectories
build-sys: use pkg-config to locate dependencies

This commit alters XRANDR (X Resize And Rotate) extension dependency,
which is expected to have at least version 1.4.  Earlier old versions of
xrandr were supported, at least to some extent.
build-sys: add test programs to .gitinore file
build-sys: unify configure.ac syntax
build-sys: use iconv library detections from gettext

This patch took copy of config.rpath from gettext 0.18.2 to build-aux/
directory.  Software projects usually does not need to do that, because
the file is copied by gettext autopoint in autogen.sh or bootstrap.

In Fluxbox case calling autopoint seems wrong, as it would generate po/
directory with necessary make automation, adn 'msgid' & 'msgstr' files,
but that is not how the translations are done in this project.
build-sys: move to non-recursive build

This rather large change will attempts to make 'make' to work better.
See excellent paper 'Recursive Make Considered Harmful' by Peter Miller
for further explanation why several make files is worse than one for
whole project.

Note.  The tests are build with 'make check' rather than defining TEST.

Reference: http://miller.emu.id.au/pmiller/books/rmch/
Reference: http://karelzak.blogspot.co.uk/2013/02/non-recursive-automake.html