resip/stack: remove magic number, should be ChunkSize

git-svn-id: https://svn.resiprocate.org/rep/resiprocate/main@10024 ddefafc4-47db-0310-ae44-fa13212b10f2
resip/stack: create new abstract class TlsBaseTransport for use by TlsTransport and soon WssTransport

git-svn-id: https://svn.resiprocate.org/rep/resiprocate/main@10025 ddefafc4-47db-0310-ae44-fa13212b10f2