Add PhotoDemon's plugin compressor to the main repository

This tool is rarely (if ever) updated, but for the sake of completeness,
I should include it in the main repository.  I use this tool to compress
PhotoDemon plugins to a custom ".pdc" format.  These compressed plugin
files are downloaded by PhotoDemon's plugin updater as necessary.
Include zLib DLL with plugin compressor
Add PhotoDemon's master language creation tool to repository

This tool is used to generate a master English-language XML file of all
user-facing text in PhotoDemon.  It is not intended for any other use,
and I have no intention of ever turning it into a general-purpose tool.

I am adding it to the main PD repository because it is an indispensable
part of the project, and I have to update it with some frequency - so I
would like changes tracked.