With out this, adding collation test files like localedata/gez_ER.UTF-8@abegede.in
does not work for locales which contain @ modifiers.
* gen-locales.mk: Make test files which contain @ modifiers in their
name work.
* localedata/gen-locale.sh: Likewise.
This patch prepares for the strcoll benchmark by moving the makefile
code for generating the locale files into a standalone snippet that
can be used elsewhere.