Fix patch such that skipping files does not count as a failure.
Previously, using -S/--skip, -f/--force, or -t/--batch to skip a patch in
a patchset still registers a failure which causes patch to return a
non-zero exit code. This is particularly undesirable with regards to
ports as there is no way to ignore the non-zero code. (Luckily, we don't
currently have any ports that make use of any of these options.)

The PR (yes, my own) is slightly incorrect: It states that -f does indeed
properly skip patches. It does, but it still sets the failure flag causing
patch to return non-zero.

PR: 19638
Submitted by: kbyanc@posi.net