libxcrypt: upgrade 4.4.28 -> 4.4.30

Changelog:
==========
* configure: Restore ucontext api functionality check.
  In c3f01c72b303cbbb0cc8983120677edee2f3fa4b the use of the ucontext api
  in the main program was removed, and with it the configure check for it.
  However, the ucontext api is still used in the "explicit_bzero" test and
  thus this test still needs to be in place.
  See also: https://bugs.gentoo.org/838172


* configure: Restore the functionality of the '--disable-symvers' switch.
  Without this fix the build was simply broken, if symbol versioning was
  disabled for any reason, e.g. whether the compiler nor the linker
  supporting it, or if disabled on purpose by the user (issue #142).
* Fix variable name in crypt(3) for a datamember of 'struct crypt_data'
  (issue #153).
* Add glibc-on-loongarch-lp64 (Loongson LA464 / LA664) entry to
  libcrypt.minver.  This was added in GNU libc 2.36.

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
(cherry picked from commit 7da5dd3b)
Signed-off-by: Steve Sakoman <steve@sakoman.com>