MWL#192: non-blocking client API, after-review fixes.

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).

include/mysql_async.h

@@ -0,0 +1,36 @@
+/* Copyright (C) 2012 MariaDB Services and Kristian Nielsen
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
+
+/* Common definitions for MariaDB non-blocking client library. */
+
+#ifndef MYSQL_ASYNC_H
+#define MYSQL_ASYNC_H
+
+extern int my_connect_async(struct mysql_async_context *b, my_socket fd,
+                            const struct sockaddr *name, uint namelen,
+                            uint timeout);
+extern ssize_t my_recv_async(struct mysql_async_context *b, int fd,
+                             unsigned char *buf, size_t size, uint timeout);
+extern ssize_t my_send_async(struct mysql_async_context *b, int fd,
+                             const unsigned char *buf, size_t size,
+                             uint timeout);
+extern my_bool my_poll_read_async(struct mysql_async_context *b,
+                                  uint timeout);
+extern int my_ssl_read_async(struct mysql_async_context *b, SSL *ssl,
+                             void *buf, int size);
+extern int my_ssl_write_async(struct mysql_async_context *b, SSL *ssl,
+                              const void *buf, int size);
+
+#endif  /* MYSQL_ASYNC_H */