GetText - something to start with

Gettext (AKA jak správně a inteligentně překládat včetně plurálů):
http://www.gnu.org/software/gettext/manual/gettext.html#Plural-forms
http://www.gnu.org/software/gettext/manual/gettext.html#Translating-plural-forms

Settlers 2.5 use some variation of gettext:
https://github.com/Return-To-The-Roots/mygettext

Linux sample:
http://stackoverflow.com/questions/1003360/complete-c-i18n-gettext-hello-world-example

WIndows guide:
http://stackoverflow.com/questions/1874509/how-to-use-gnu-gettext-with-ms-visual-c

PO files editor:
http://poedit.net/