Fix building without libedit

Signed-off-by: Travis Cross <tc@traviscross.com>

FS-353
Add comment to distant #endif

FS-353
libsndfile windows update version string
Make debian/README files more markdown-like
Update, organize, and improve debian/README.source
Clean up introduction
Reorganize sections in debian/README.source
Describe workaround in Debian/README.source

Pre-jessie versions of Debian's mk-build-deps tool rely on libraries
that do not correctly parse debian/control, so we have to clip it down
to a smaller subset of the format to build on e.g. wheezy.
Add note about the supported Debian release for building