Comment 0 for bug 1220467

When using libdrizzle in nonblocking mode, there's no way for the caller to know whether to wait for readability or writability on the socket when libdrizzle returns DRIZZLE_RETURN_IO_WAIT.

(Often it'll be waiting for readability, but it needs to wait for writability if you're sending a long query or bound parameter, or using SSL, or doing nonblocking connect.)

I can think of three obvious ways to extend the libdrizzle api to fix this:

- add a function drizzle_fd_waiting_for() (but with a better name) that returns POLLIN, POLLOUT, etc
- change drizzle_fd() to return both the fd and the current flags
- split DRIZZLE_RETURN_IO_WAIT into two return codes, DRIZZLE_RETURN_IO_READ and DRIZZLE_RETURN_IO_WRITE