Log OpenSSL version in ./configure output

This information is useful to know when scanning buildfarm results, and
it is already displayed in Meson.  The output of `openssl version` is
logged, with the command retrieved from PATH.

This depends on c8e4030d1b, so backpatch down to 16.

Reviewed-by: Peter Eisentraut, Daniel Gustafsson, Tom Lane
Discussion: https://postgr.es/m/ZTW9yOlZaSVoFhTz@paquier.xyz
Backpatch-through: 16

configure

@@ -14179,6 +14179,9 @@ $as_echo_n "checking for OPENSSL... " >&6; }
 $as_echo "$OPENSSL" >&6; }
 fi
 
+pgac_openssl_version="$($OPENSSL version 2> /dev/null || echo openssl not found)"
+{ $as_echo "$as_me:${as_lineno-$LINENO}: using openssl: $pgac_openssl_version" >&5
+$as_echo "$as_me: using openssl: $pgac_openssl_version" >&6;}
 if test "$with_ssl" = openssl ; then
   ac_fn_c_check_header_mongrel "$LINENO" "openssl/ssl.h" "ac_cv_header_openssl_ssl_h" "$ac_includes_default"
 if test "x$ac_cv_header_openssl_ssl_h" = xyes; then :

configure.ac

@@ -1571,6 +1571,8 @@ if test "$with_gssapi" = yes ; then
 fi
 
 PGAC_PATH_PROGS(OPENSSL, openssl)
+pgac_openssl_version="$($OPENSSL version 2> /dev/null || echo openssl not found)"
+AC_MSG_NOTICE([using openssl: $pgac_openssl_version])
 if test "$with_ssl" = openssl ; then
   AC_CHECK_HEADER(openssl/ssl.h, [], [AC_MSG_ERROR([header file <openssl/ssl.h> is required for OpenSSL])])
   AC_CHECK_HEADER(openssl/err.h, [], [AC_MSG_ERROR([header file <openssl/err.h> is required for OpenSSL])])