scanbd Code

Add AM_MAINTAINER_MODE in configure.ac to avoid rebuild of the automake
generated files as svn does not preserve timestamps on generated files

Updated trigger section of manpage

Fix testscanbuttond path to backends.
This will still not work for the autoconf based build system as
The dlls are built at install time only

- More updates to the manpage
- Added systemd integration files

Add optinal debuglevel option to -d/--debug

Fixes to Makefile.simple (install & doc sections)

Corrected shebang in contrib/action.script

- Split device snippets from scanbd.conf into a file per device in scanners.d
- Added to above to Makefile.am and Makefile.simple
- Rewrite of slog to use vsnprintf() to replace the main loop

- Updated syntax in the synopsis of the manpage
- some minor corrections to the manpage

- added comments in Makefile.conf(.in) so that it is clear that Makefile.conf should not be hand-edited
- Fixed slog.c to avoid overlapping destination and arguments, the result is undefined according to C99