move parsenum tests
more explicit STR_SIZE("0x0000") is more explicit than a 6 from no where
use __progname instead of hardcoded names
add macros for flags, more convenient
usort: improvements and regressions
* option --sort handled
* option -t or --field-separator implemented
* can sort on a *single* specific field instead of the whole line
* added month sorting (on their full name, like "Janvier" - ICU format: MMMM)
* number sorting (temporary - easy to restore) lost
* for now, -u option is implied