Cygwin: Use cmdsynopsis element in utils documentation

Cygwin: Use cmdsynopsis element in utils documentation

Use <cmdsynopsis> element markup in utils docbook documentation, rather
than some preformatted text inside <screen>.

(This didn't happen as part of 646745cb, when we first started using
refentry elements to make it possible to generate manpages)

This helps produce better looking manpages:

* uses bold (for command names) and italic (for replaceable items)
* different output formats inconsistently treat tabs inside <screen>
(so we have to be careful to not use them in that preformatted text)

Also clean up various issues:

* Replace '[OPTIONS]' with a real synopsis of the options
* Consistently use 'ITEM...' rather than 'ITEM1 [ITEM2...]' for an item
which should appear 1 or more times (cygcheck -f, getfacl, kill)
* Consistently document the '-h | -V' invocation form
* Since replaceable items are now marked up so they have some formatting
indicating they are replaceable, we can drop wrapping them in angle
brackets, as is done in some places
* Add missing '-W' and '-p PID' options to ps synopsis
* Adjust cygpath synopsis to show that only one 'System information'
option is allowed, possibly modified by -A

Future work:
* Sync up the actual help emitted by the util, where it's been improved
* Also don't use <screen> for formatting 'OPTIONS' section of manpage
* pldd inconsistently uses '-?' rather than '-h'!