Previously, our default lock model kind of assumed that every lock was
potentially a read-write lock. This was a poor choice, since
read-write locks are far more expensive than regular locks, and so the
lock API should only use them when we can actually take advantage of
them. Neither our pthreads or win32 lock implementation provided rw
locks.
Now that we have a way (not currently used!) to indicate that we
really want a read-write lock, we shouldn't actually say "lock this
for reading" or "lock this for writing" unless we mean it.
This bug was introduced by the code to make the backend able to safely release the base lock while calling select().
Also, we change win32select.c to the same 32-fds-to-start default as the rest of the backends, so that the main/many_events test can test it. It was at 64-to-start, so the test wasn't hitting it.
svn:r1513
