doc: Do not process .in files for html

doc: Do not process .in files for html

We do not want to process .pod.in files when generating HTML versions
of the man pages. Change the filename filtering logic to only accept
.pod files, so we'll also skip over all other stuff we don't want,
like CVS or fragments directories.

Change-Id: Ic7da67dd5297aa52a67a8a0dc0b9cc7904cfa2b4
Reviewed-on: http://gerrit.openafs.org/3302
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>