manpage: improve locale setup in example .xsession (Thanks Harald König)

manpage: improve locale setup in example .xsession (Thanks Harald König)

Harald mentioned he was surprised about the locales we recommend in the
.xsession example, so I’ve re-investigated.

Here is the test program I have used:

    #include <stdio.h>
    #include <locale.h>

    int main() {
        /* SUSv2 setlocale(3) says:
         * Internationalised programs must call setlocale() to initiate
         * a specific language operation. This can be done by calling
         * setlocale() as follows: */
        setlocale(LC_ALL, "");

        printf("LC_NUMERIC is %s\n", setlocale(LC_NUMERIC, NULL));
    }

Then, I have unset LANG and LC_*:

    midna /tmp $ env | grep LANG
    midna /tmp $ env | grep LC
    midna /tmp $

Now, observe that LC_ALL overwrites all specific LC variables:

    midna /tmp $ LC_ALL=de_DE.UTF-8 LC_NUMERIC=en_DK.UTF-8 ./localetest
    LC_NUMERIC is de_DE.UTF-8

However, LANG does not:

    midna /tmp $ LANG=de_DE.UTF-8 ./localetest
    LC_NUMERIC is de_DE.UTF-8
    midna /tmp $ LANG=de_DE.UTF-8 LC_NUMERIC=en_DK.UTF-8 ./localetest
    LC_NUMERIC is en_DK.UTF-8

This is consistent with what perldoc perllocale says:
http://perldoc.perl.org/perllocale.html#ENVIRONMENT