btowc: fix missing file Detected by ./gnulib-tool --test btowc. configure.ac:111: warning: gt_LOCALE_FR is m4_require'd but not m4_defun'd glm4/btowc.m4:7: gl_FUNC_BTOWC is expanded from... configure.ac:27: gl_INIT is expanded from... configure.ac:111: the top level * modules/btowc (Files): Also ship locale-fr.m4. Signed-off-by: Eric Blake <eblake@redhat.com>