Support sending and receiving messages in different size packet buffers
Fix problem with receiving multiple UDP packets in loop
Remove override definition of PJSIP_MAX_PKT_LEN
More efficient buffering on TCP and TLS transport
Fix spacing issues for merge back
Sort out more white-space diff issues
Fix remaining (hopefully) whitespace diff issues
Fix remaining (hopefully) whitespace diff issues - take 2
Change default normal message size to 4000 to match old default maximum size
Merge pull request #20 from Metaswitch/two_size_messages

[Reviewer Andy] Two size messages