Update .gitignore, delete generated files

configure and config.h.in were in .gitignore but still in git,
and .gitignore was missing some other generated files.
Use autotools to propagate the version

Also, use git to set the version.
Clean up `make dist`

configure.ac shouldn't be excluded, some generated files and .git
should be.

Respect DESTDIR and put distfiles in DESTDIR/dist instead of ..

Cosmetics: rename EXCLUDE to .distignore
Add more sophisticated BDB detection

Based on http://www.gnu.org/software/autoconf-archive/ax_path_bdb.html
Clean up definition of local build variables
Fix checks for other libraries

Use a generic macro to reduce code repetition.

Package maintainers can now use FOO_CPPFLAGS and FOO_LDFLAGS to set the
library and header locations, e.g.
LIBSASL_LDFLAGS=-L/usr/lib64/sasl2

This removes the hardcoded assumption that if we find /path/include/foo.h
the corresponding library is in /path/lib/, which isn't always the case.
libsnet: import git HEAD from sourceforge
libsnet: move libtool.m4 into m4/ subdir
libsnet: Use AX_WITH_LIBRARY
libsnet: Hardcode the values of HAVE_* in snet.h

Changing these after installation should be impossible.
C is not a dynamic language.
libsnet: Move dependency includes into snet.h
libsnet: Add multiple inclusion guard
libsnet: switch to automake

libsnet was already using libtool, and using libtool without automake
is unsupported. Fixes build on CentOS/RHEL.

Probably breaks some things like Mac OS X support, but I'm too lazy to
fix that at the moment and we don't need it.
Add check for zlib

libsnet automatically links against zlib if it's present,
so simta should as well. --with-zlib=no will still disable it,
but builds that don't specify will actually work.
Change handling of userid

Allow runtime configuration of the non-privileged username.

Add an option to disable setting the ownership of installed files, as
this conflicts with many packaging systems that expect and desire to
run 'make install' as a non-privileged user.
Change handling of pidfile

Make the location configurable at runtime and don't try to create it
during installation (that makes no sense).
rpm: Add spec file and RH init script
Move LFS script to packaging/