After the merge of VIO stuff from MySQL 5.6, there were some bugs left
in the non-blocking client library:
- vio_io_wait() was introduced without any support for non-blocking operation,
so async queries could turn into sync.
- Timeouts were changed to milliseconds, but this was not reflected in the
non-blocking API, also semantics was changed so signed -1 was used for
"no timeout" rather than unsigned 0.
Fix by implementing and using my_io_wait_async() in the non-blocking case. And
by introducing a new mysql_get_timeout_value_ms() API function that provides
the timeout with millisecond granularity. The old mysql_get_timeout_value()
is kept and fixed to work correctly, converting the timeout to whole seconds.
Main change is that non-blocking operation is now an option that must be
explicitly enabled with mysql_option(mysql, MYSQL_OPT_NONBLOCK, ...)
before any non-blocing operation can be used.
Also the CLIENT_REMEMBER_OPTIONS flag is now always enabled and thus
effectively ignored (it was not really useful anyway, and this simplifies
things when non-blocking mysql_real_connect() fails).
