Bugfix: if a SYN is received in the SYN_RCVD state we should not send a blank SYN, but a SYNACK in response.
Bugfix: correctly handle the case if uip_sappdata is NULL.
Allow the default TTL to be configured with UIP_CONF_TTL
Produce an error if the UIP_TCP_MSS is too large for UIP_BUFSIZE
Merge pull request #457 from adamdunkels/push/uip6-bugfixes

IPv6 bugfixes
Merge remote-tracking branch 'upstream/master'