Mapping to System Call values

Re: My previous message, I had a thought several minutes after i sent it:

What about changing the C code in support/fcntl.c so that before it
calls fcntl it'll map the C-sharp fcntlcommand values from their
existing values to whatever the system header file values are for it.

IF this is reasonable to do, i will try to do it today or tomorrow. 
Just have to :
(1) Of course, create a branch
(2) Put this in (probably as a support function called before each call
to fcntl)
and
(3) At minimum test on both Mac and Linux.

If someone wants to stop me in my tracks before i do this to say it's a
bad idea, i'm ok with that.

-Rob