We can parse KAME's SADB_ACQUIRE message, but cannot handle the reply (yet)
Ignore some OSX and llvm output
sync
Add initial support for SADB_ACQUIRE on KAME platforms (tested on OSX).

Instead of looking up the active flow for an ACQUIRE message based on
the OpenBSD-specific FLOW_SRC/FLOW_DST extensions, the KAME stack sets
an unique policy Id for each new flow and sends it in the ACQUIRE
message to look up the active flows.
Also flush the SPD in addition to the SADB on startup.