resolv: Move ns_name_unpack to its own file and into libc

Reformat to GNU style. Avoid out-of-bounds buffer arithmetic.
Eliminate the labellen function.

The symbol was moved using scripts/move-symbol-to-libc.py.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist

@@ -2583,6 +2583,7 @@ GLIBC_2.34 mtx_timedlock F
 GLIBC_2.34 mtx_trylock F
 GLIBC_2.34 mtx_unlock F
 GLIBC_2.34 ns_name_ntop F
+GLIBC_2.34 ns_name_unpack F
 GLIBC_2.34 openpty F
 GLIBC_2.34 posix_spawn_file_actions_addclosefrom_np F
 GLIBC_2.34 pthread_attr_getaffinity_np F
@@ -3030,6 +3031,7 @@ GLIBC_2.9 getutxline F
 GLIBC_2.9 inotify_init1 F
 GLIBC_2.9 login F
 GLIBC_2.9 ns_name_ntop F
+GLIBC_2.9 ns_name_unpack F
 GLIBC_2.9 pipe2 F
 GLIBC_2.9 pututline F
 GLIBC_2.9 pututxline F

sysdeps/unix/sysv/linux/s390/s390-32/libresolv.abilist

@@ -82,7 +82,6 @@ GLIBC_2.9 ns_name_pton F
 GLIBC_2.9 ns_name_rollback F
 GLIBC_2.9 ns_name_skip F
 GLIBC_2.9 ns_name_uncompress F
-GLIBC_2.9 ns_name_unpack F
 GLIBC_2.9 ns_parse_ttl F
 GLIBC_2.9 ns_parserr F
 GLIBC_2.9 ns_put16 F

sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist

@@ -2391,6 +2391,7 @@ GLIBC_2.34 mtx_timedlock F
 GLIBC_2.34 mtx_trylock F
 GLIBC_2.34 mtx_unlock F
 GLIBC_2.34 ns_name_ntop F
+GLIBC_2.34 ns_name_unpack F
 GLIBC_2.34 openpty F
 GLIBC_2.34 posix_spawn_file_actions_addclosefrom_np F
 GLIBC_2.34 pthread_attr_getaffinity_np F
@@ -2826,4 +2827,5 @@ GLIBC_2.9 dup3 F
 GLIBC_2.9 epoll_create1 F
 GLIBC_2.9 inotify_init1 F
 GLIBC_2.9 ns_name_ntop F
+GLIBC_2.9 ns_name_unpack F
 GLIBC_2.9 pipe2 F

sysdeps/unix/sysv/linux/s390/s390-64/libresolv.abilist

@@ -77,7 +77,6 @@ GLIBC_2.9 ns_name_pton F
 GLIBC_2.9 ns_name_rollback F
 GLIBC_2.9 ns_name_skip F
 GLIBC_2.9 ns_name_uncompress F
-GLIBC_2.9 ns_name_unpack F
 GLIBC_2.9 ns_parse_ttl F
 GLIBC_2.9 ns_parserr F
 GLIBC_2.9 ns_put16 F