Added support for data files internationalization by a simple 3 lines code in lisprea...

Added support for data files internationalization by a simple 3 lines code in lispreader's read_string().
To translate a level's title to European Portuguese, I would look at:
(title "Hello World!")
and add:
(title-pt_PT "Ol� Mundo!")

Also, made display_text_file() using lispreader (to make it i18n too). Unfortunately, there is a crash of lisp_reader in my system (not related), so I wasn't able to give it a try.
data/*.txt files also need updating to work. Else, it should just skip it, without crashing.

SVN-Revision: 1537