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: I246000a9323852d0aeefd7e7357eeece4daa3346
Reviewed-on: http://gerrit.openafs.org/3302
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-on: http://gerrit.openafs.org/3930
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>