This incorporates:
2017-11-14 [BZ #10871] Implement alternative month names
2017-11-14 [BZ #10871] Abbreviated alternative month names (%Ob)
2017-06-20 Use locale_t, not __locale_t, throughout glibc
* lib/nstrftime.c (ABALTMON_1) [!COMPILE_WIDE]: New macro.
(LOCALE_PARAM) [_LIBC && USE_IN_EXTENDED_LOCALE_MODEL]:
Use locale_t, not __locale_t.
(a_altmonth, f_altmonth, aam_len) [_NL_CURRENT]: New macros.
(__strftime_internal): Add support for alternate months.