Update: Socket size_read/size_write checks, result == -1, and explicit passing .generic.

Update: Socket size_read/size_write checks, result == -1, and explicit passing .generic.

Make sure size_read and size_write are not 0.
If either is 0, then return F_data_not.

Make sure the result checks are "== -1" rather than "< 0".

Explicitly pass .generic for the address union.
This probably isn't necessary but being explicit seems safer.
The memory address of the address union, regardless of the union type being used, is cast to 'struct sockaddr' in most cases.
This makes the use of ".generic" very practical.

Add documentation comment about F_pipe being returned.

Problems with the address unions ".sin_family" must be set or unclear F_pipe errors are returned.
I may in a future commit perform this assignment during setup because the "form" parameter makes this practical and reasonable to do.