res_rtp_asterisk: Fix undefined function when PJPROJECT is not installed

The dtls_perform_handshake function was mistakenly placed under the guards for
USE_PJPROJECT. If PJPROJECT was not installed, the function would not be
defined, while other functions would attempt to still use it. This prevented
res_rtp_asterisk from being loaded.

ASTERISK-24001 #close
Reported by: Don Fanning


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@418172 f38db490-d61c-443f-a65b-d21fe96a405b
manager/ARI: Update version to 2.4.0/1.4.0; Update UPGRADE.txt


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@418182 f38db490-d61c-443f-a65b-d21fe96a405b