error, strerror-override: Support new errno values from POSIX:2008.

error, strerror-override: Support new errno values from POSIX:2008.

* m4/errno_h.m4 (gl_HEADER_ERRNO_H): Test also EOWNERDEAD and
ENOTRECOVERABLE.
* lib/errno.in.h (EOWNERDEAD, ENOTRECOVERABLE): Define on all
platforms.
* lib/strerror-override.c (strerror_override): Conditionalize the
EOWNERDEAD, ENOTRECOVERABLE handling on GNULIB_defined_EOWNERDEAD.
* lib/strerror-override.h (strerror_override): Declare also if
GNULIB_defined_EOWNERDEAD is defined.
* tests/test-errno.c (e130, e131): New variables.
* doc/posix-headers/errno.texi: Mention the status for EOWNERDEAD,
ENOTRECOVERABLE.
Reported by Paolo Bonzini.