created script to check the list of source files to handle for translation
Because the source file is redefined in the 'po/' directories, there is a
possibility that they get misaligned.
There is now a script that will check everything is in line; it is
triggered by "make check".
The case of the "util/" stuff is excluded at current time because the way
they are defined makes it hard to properly deduce the correct list of
sources, and it is not worth, the core need being on wmaker and WPrefs.
Signed-off-by: Christophe CURIS <christophe.curis@free.fr>