Detect busybox logger and change logger cmdline

The busybox logger command (used on embedded systems and such) does not
support the -i option and die squaking if it's used. If the logger
configured is a symlink to busybox, the -i option must not be used.
rsnapshot-diff: Fixed removed files reported as addition (+ mark)

Fix an obvious copy/paste mistake in rsnapshot-diff.pl introduced
by 00e2f5085bd476ab867595d0ecbbed71264e9b5f
Fixed pod2man location.

Uses the pod2man present in the user path. Especially usefull if the
user has perl & pod2man installed in /usr/local/
Add allow_failed_sync option parsing and logic.
Add allow_failed_sync to default config.
Automatic update.
Revert "Automatic update."

This reverts commit 5f5a7e68e3bbdfd82802c16156fd8bbd647d29ca.
Fix "Use of uninitialized value" warnings.
Merge branch 'master' of https://github.com/DrHyde/rsnapshot