The current definitions were mostly useful to glibc and followed its
feature_test_macros(3) documentation.
However, this means other platforms still had problems when building with
strict compilation flags. _BSD_SOURCE, for example, is only recognized by
glibc, and other platforms sometimes need _XOPEN_SOURCE instead, or even the
removal of some definitions (such as the outdate _POSIX_SOURCE one).
_POSIX_SOURCE also had to be conditionally defined in some places, as what
it enables or disables during compilation varies across systems.
No functional changes. All files used by _both_ libvncserver and
libvncclient are put into a 'common' directory and references
from other files as well as Autotools and CMake build systems are
updated.
Signed-off-by: Christian Beier <dontmind@freeshell.org>