Improve recv_msg support.

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>
Remove setsockopt and replace with generic get_handle()

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>
Add Allocating template and make a load of allocation code common.

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>
Tidy up internal allocators for proactors

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>
Clean up the proactor thunk code.

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>
Handle empty environments

Signed-off-by: Rick Taylor <rick@tropicalstormsoftware.com>