updatemanpages.pl: Update man pages to use current date and versions

Added script to update man pages to use the current date and
curl/libcurl versions.

updatemanpages.pl has three arrays: list of directories to look in,
list of extensions to process, list of files to exclude from
processing.

Check man page in git repoistory using the date from the existing man
page before updating to avoid updating the man page if no change is
made.

If data is received from the git command then update the man page with
the current date and version otherwise leave alone.

Applied patch from badger to make the date argument optional, change the
git command used, added date argument to processfile subroutine and
print to STDERR if no date is found in a man page.

Added code to process the changed man page into a new man page with
.dist added to the filename to keep the original source files unchanged.
Updated POD documentation to reflect that the date argument optional.

Code style is in line with CODE_STYLE.md.

Directo...