Add support for using SOCKS proxies

Added a new SOCKSProxySocketFactory class that can be used to allow
establishing LDAP and LDAPS connections through a SOCKSv4 or SOCKSv5
proxy server.  Communication with the SOCKS proxy server itself must
be unencrypted (although communication with the target LDAP server
may optionally be end-to-end encrypted with TLS), and the SOCKS
proxy server must not require authentication.

docs/release-notes.html

@@ -34,6 +34,15 @@ <h3>Version 6.0.9</h3>
                   <br><br>
                 </li>
 
+                <li>
+                  Added a new SOCKSProxySocketFactory class that can be used to allow establishing
+                  LDAP and LDAPS connections through a SOCKSv4 or SOCKSv5 proxy server.
+                  Communication with the SOCKS proxy server itself must be unencrypted (although
+                  communication with the target LDAP server may optionally be end-to-end encrypted
+                  with TLS), and the SOCKS proxy server must not require authentication.
+                  <br><br>
+                </li>
+
                 <li>
                   Updated the ldif-diff tool to add a --byteForByte argument that can be used to
                   indicate that it should not ignore differences between source and target entries

messages/unboundid-ldapsdk-util.properties

@@ -1250,3 +1250,6 @@ ERR_GET_NON_BC_FIPS_CLASS_LOADER_ERROR_FINDING_JARS=Unable to create a class \
 ERR_GET_NON_FIPS_BC_CLASS_LOADER_NO_JARS_FOUND=Unable to create a class \
   loader for accessing non-FIPS-compliant Bouncy Castle functionality because \
   the expected Bouncy Castle library was not found in the ''{0}'' directory.
+ERR_SOCKS_PROXY_SF_CANNOT_CREATE_UNCONNECTED_SOCKET=Unable to create an \
+  unconnected socket for communication through a SOCKS proxy server when an \
+  SSLSocketFactory has been configured.