scanbd Code

- 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

Added Makefile.simple for dosc directory
Moved generation of Makefile.conf to Makefile.am: if we generate
it from configure, it gets deleted with "make distclean"

Re-generate Makefile.conf from configure so that it get the correct package name
and version from configure.ac

- added a man page
- include Makefile.simple in Makefile.am so that it gets included in the tar-file with make dist

- The meta backend would always look for the meta.so file in the directory it was compiled for
Added a callback to scanbd to retrieve the location where the backends are stored
- Reverted split of scanbuttond config dir and lib dir. Use lib dir only
- Major cleanup of Makefile.simple: added Makefile.conf that contains all configuration
This is included from all applicable Makefile.simple
- Rewrote install section of Makefile.simple. Adapted it to latest configuartion and
made it aware of whether scanbuttond is used and only install backends when applicable

This fix should solve the linking issues also on *BSD (tested on FreeBSD)

Fix linking issue for scanbuttond backends

- Do not try to load scanbuttond backend .so files from scanbuttond_backends_dir, use the fixed library path
- Corrected path where store backends

Moved expansion of the script variable to an absolute path in oder to avoid a memory leak