bug#50726: 26.3; Let `count-words(-region)' count only words entirely within the region

[Drew Adams <drew.adams@oracle.com>]

Enhancement request.

A word that straddles the beginning or end of the region is counted as a
word in the region.  It would be good to be able to have such functions
not count such partial words.
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Here's an example of a command that counts the words in a rectangular
region.  By default it excludes words that straddle the row boundaries,
but a prefix arg counts such partial words also.

https://emacs.stackexchange.com/a/68611/105
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Admittedly, this difference is not so important for a non-rectangular
region, as it has only two boundaries, and a user can see interactively
whether the text at the beginning or end forms a real word.  But when
called from Lisp, if you want to exclude such partial words you need to
write some code to adjust the count.

In GNU Emacs 26.3 (build 1, x86_64-w64-mingw32)
 of 2019-08-29
Repository revision: 96dd0196c28bc36779584e47fffcca433c9309cd
Windowing system distributor `Microsoft Corp.', version 10.0.19042
Configured using:
 `configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''