Deprecate a.out support for NetBSD targets.

As discussed previously, a.out support is now quite deprecated, and in
some cases removed, in both Binutils itself and NetBSD, so this legacy
default makes little sense. `netbsdelf*` and `netbsdaout*` still work
allowing the user to be explicit about there choice. Additionally, the
configure script warns about the change as Nick Clifton requested.

One possible concern was the status of NetBSD on NS32K, where only a.out
was supported. But per [1] NetBSD has removed support, and if it were to
come back, it would be with ELF. The binutils implementation is
therefore marked obsolete, per the instructions in the last message.

With that patch and this one applied, I have confirmed the following:

--target=i686-unknown-netbsd
--target=i686-unknown-netbsdelf
  builds completely

--target=i686-unknown-netbsdaout
  properly fails because target is deprecated.

--target=vax-unknown-netbsdaout builds completely except for gas, where
the target is deprecated.

[1]: https://mail-index.netbsd.org/tech-toolchain/2021/07/19/msg004025.html

config/ChangeLog:

	* picflag.m4: Simplify SHmedia NetBSD match by presuming ELF.

gcc/ChangeLog:

	* configure: Regenerate.

libada/ChangeLog:

	* configure: Regenerate.

libgcc/ChangeLog:

	* configure: Regenerate.

libiberty/ChangeLog:

	* configure: Regenerate.

config/picflag.m4

@@ -63,9 +63,7 @@ case "${$2}" in
     sh-*-linux* | sh[[2346lbe]]*-*-linux*)
 	$1=-fpic
 	;;
-    # FIXME: Simplify to sh*-*-netbsd*?
-    sh-*-netbsdelf* | shl*-*-netbsdelf* | sh5-*-netbsd* | sh5l*-*-netbsd* | \
-      sh64-*-netbsd* | sh64l*-*-netbsd*)
+    sh*-*-netbsd*)
 	$1=-fpic
 	;;
     # Default to -fPIC unless specified otherwise.

gcc/configure

@@ -5480,9 +5480,7 @@ case "${target}" in
     sh-*-linux* | sh[2346lbe]*-*-linux*)
 	PICFLAG_FOR_TARGET=-fpic
 	;;
-    # FIXME: Simplify to sh*-*-netbsd*?
-    sh-*-netbsdelf* | shl*-*-netbsdelf* | sh5-*-netbsd* | sh5l*-*-netbsd* | \
-      sh64-*-netbsd* | sh64l*-*-netbsd*)
+    sh*-*-netbsd*)
 	PICFLAG_FOR_TARGET=-fpic
 	;;
     # Default to -fPIC unless specified otherwise.
@@ -19888,7 +19886,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 19891 "configure"
+#line 19889 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -19994,7 +19992,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 19997 "configure"
+#line 19995 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H

libada/configure

@@ -3231,9 +3231,7 @@ case "${host}" in
     sh-*-linux* | sh[2346lbe]*-*-linux*)
 	PICFLAG=-fpic
 	;;
-    # FIXME: Simplify to sh*-*-netbsd*?
-    sh-*-netbsdelf* | shl*-*-netbsdelf* | sh5-*-netbsd* | sh5l*-*-netbsd* | \
-      sh64-*-netbsd* | sh64l*-*-netbsd*)
+    sh*-*-netbsd*)
 	PICFLAG=-fpic
 	;;
     # Default to -fPIC unless specified otherwise.

libgcc/configure

@@ -2422,9 +2422,7 @@ case "${host}" in
     sh-*-linux* | sh[2346lbe]*-*-linux*)
 	PICFLAG=-fpic
 	;;
-    # FIXME: Simplify to sh*-*-netbsd*?
-    sh-*-netbsdelf* | shl*-*-netbsdelf* | sh5-*-netbsd* | sh5l*-*-netbsd* | \
-      sh64-*-netbsd* | sh64l*-*-netbsd*)
+    sh*-*-netbsd*)
 	PICFLAG=-fpic
 	;;
     # Default to -fPIC unless specified otherwise.

libiberty/configure

@@ -5368,9 +5368,7 @@ case "${host}" in
     sh-*-linux* | sh[2346lbe]*-*-linux*)
 	PICFLAG=-fpic
 	;;
-    # FIXME: Simplify to sh*-*-netbsd*?
-    sh-*-netbsdelf* | shl*-*-netbsdelf* | sh5-*-netbsd* | sh5l*-*-netbsd* | \
-      sh64-*-netbsd* | sh64l*-*-netbsd*)
+    sh*-*-netbsd*)
 	PICFLAG=-fpic
 	;;
     # Default to -fPIC unless specified otherwise.