acinclude: add additional libraries to check for LDAP support

- Add an additional check for LDAP that also checks for OpenSSL since
  on AIX those libraries may be required to link LDAP properly.

Fixes https://github.com/curl/curl/issues/3595
Closes https://github.com/curl/curl/pull/3596

acinclude.m4

@@ -791,7 +791,9 @@ AC_DEFUN([CURL_CHECK_LIBS_LDAP], [
     '-lldap -llber' \
     '-llber -lldap' \
     '-lldapssl -lldapx -lldapsdk' \
-    '-lldapsdk -lldapx -lldapssl' ; do
+    '-lldapsdk -lldapx -lldapssl' \
+    '-lldap -llber -lssl -lcrypto' ; do
+
     if test "$curl_cv_ldap_LIBS" = "unknown"; then
       if test -z "$x_nlibs"; then
         LIBS="$curl_cv_save_LIBS"