Adding (ice-9 suspendable-ports) support to https / custom ports

[Christopher Allan Webber]

Hiya,

For the project I'm working on, I'll need to have (ice-9
suspendable-ports) work with https.  This is a bit more urgent than I
realized.  I'm willing to attempt the work, but I don't even know where
to start.

Could someone give me pointers as to where to begin spelunking?  I'm
guessing I have to both follow the lead of the suspendable-ports
adjustments to normal ports and also enable fnctl support for custom
ports?  Specifically, I imagine that this needs to be supported:

     (let ((flags (fcntl socket F_GETFL)))
       (fcntl socket F_SETFL (logior O_NONBLOCK flags)))

Either that or we need some generalized procedure that can either do
this to a port which does set fnctl or... I don't know what it would do
for something which doesn't need to run that operation.

Advice appreciated!
 - Chris