adjust .md files to make lexgrog happy

adjust .md files to make lexgrog happy

the whatis(1) tool cannot parse the bup manpages, because there
are two words before the '-' separator. This patch joins the words
using another '-', in the same fashion as git, to overcome this
limitation.

Before:

$ whatis bup fuse
bup (1)              - Backup program using rolling checksums and git file fo...
fuse: nothing appropriate.
$ whatis bup-fuse
bup-fuse: nothing appropriate.

After:

$ whatis bup-fuse
bup-fuse (1)         - mount a bup repository as a filesystem

Signed-off-by: Jon Dowland <jmtd@debian.org>