resolv: Move dn_skipname to its own file and into libc

And reformat it to GNU style.

dn_skipname is used outside glibc, so do not deprecate it,
and export it as dn_skipname (not __dn_skipname).  Due to internal
users, provide a __libc_dn_skipname alias, and keep __dn_skipname
as a pure compatibility symbol.

__dn_skipname@GLIBC_2.0 was moved using the script, and
dn_skipname@@GLIBC_2.34 was added using make update-all-abi.

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

sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist

@@ -128,6 +128,7 @@ GLIBC_2.0 __deregister_frame F
 GLIBC_2.0 __deregister_frame_info F
 GLIBC_2.0 __dgettext F
 GLIBC_2.0 __dn_comp F
+GLIBC_2.0 __dn_skipname F
 GLIBC_2.0 __dup2 F
 GLIBC_2.0 __environ D 0x4
 GLIBC_2.0 __errno_location F
@@ -2554,6 +2555,7 @@ GLIBC_2.34 dlsym F
 GLIBC_2.34 dlvsym F
 GLIBC_2.34 dn_comp F
 GLIBC_2.34 dn_expand F
+GLIBC_2.34 dn_skipname F
 GLIBC_2.34 execveat F
 GLIBC_2.34 forkpty F
 GLIBC_2.34 gai_cancel F

sysdeps/unix/sysv/linux/sparc/sparc32/libresolv.abilist

@@ -1,7 +1,6 @@
 GLIBC_2.0 __b64_ntop F
 GLIBC_2.0 __b64_pton F
 GLIBC_2.0 __dn_count_labels F
-GLIBC_2.0 __dn_skipname F
 GLIBC_2.0 __fp_nquery F
 GLIBC_2.0 __fp_query F
 GLIBC_2.0 __fp_resstat F

sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist

@@ -3,6 +3,7 @@ GCC_3.0 __deregister_frame_info_bases F
 GCC_3.0 __register_frame_info_bases F
 GCC_3.0 __register_frame_info_table_bases F
 GLIBC_2.0 __dn_comp F
+GLIBC_2.0 __dn_skipname F
 GLIBC_2.0 dladdr F
 GLIBC_2.0 dlclose F
 GLIBC_2.0 dlerror F
@@ -2389,6 +2390,7 @@ GLIBC_2.34 dlsym F
 GLIBC_2.34 dlvsym F
 GLIBC_2.34 dn_comp F
 GLIBC_2.34 dn_expand F
+GLIBC_2.34 dn_skipname F
 GLIBC_2.34 execveat F
 GLIBC_2.34 forkpty F
 GLIBC_2.34 gai_cancel F

sysdeps/unix/sysv/linux/sparc/sparc64/libresolv.abilist

@@ -1,7 +1,6 @@
 GLIBC_2.0 __b64_ntop F
 GLIBC_2.0 __b64_pton F
 GLIBC_2.0 __dn_count_labels F
-GLIBC_2.0 __dn_skipname F
 GLIBC_2.0 __fp_nquery F
 GLIBC_2.0 __fp_query F
 GLIBC_2.0 __fp_resstat F