The files that need to be translated are:
prmdlgen.dlg
stren.rc
lswitch.ipf
Readme
lswres.h
This file need the new language code added (ie EN = 1)
It also needs the language name in your native language
These entries are near the top of the file and how to 
do it should be self explanatory

The ,msg and ,def files are no longer used.

The following is for the developer so they remember 
what to update. (a translator can do part or all of this if 
they wish but thats not necessary)

lswitch.rc master rc file
You need to include prmdlgxx.dlg strxx.rc in this file
see the other language includes at the bottom of the file

lswresen.lnk.tpl
Change the lang and country code in the build level string
Change the "name" string and .tpl file name to reflect the 
new language

makefile.en
Change the LANGUAGE = and file ext to reflect the new 
language.

root directory makefile
Add the wmake command to call the new makefile.xx
It is under the Resource target
The -a must be in the command line

docs/makefile
Add the new language following the pattern used for ES
We may need to generate a new xx_XX.nls file to put
in the wipfc directory.

Code updates needed.
Grep root for CZ. Then add the new language and if 
needed code page everywhere it occurs following the
pattern of the existing code. If a new code page is
added the unicode stuff in the misc dialog needs updating
UniCreateUconvObject((UniChar *)L"IBM-852", &uconv_object852);

Update the scan codes in lswres.h to make the hotkeys
work. All menu items must have unique mnemonics and
the hotkeys and mnemonics must match. It is probably
easier to use Alex's qe editor for the non 850 languages