MDEV-4021 : Enable Ctrl-C handler when reading password, on Windows.
MDEV-4021 : Enable Ctrl-C handler when reading password, on Windows.

Prior to this patch, _getch() was used to read password input from console. getch() has a property that it reads Ctrl-C as character with ASCII code 0x03, and disregards Ctrl-C handler for  current process. 
The fix is to use ReadConsole() API instead of getch() , after setting console mode to ENABLE_PROCESSED_INPUT - this mode allows current process to handle Ctrl-C events.

davidl-zend/zenddbi,ollie314/server,davidl-zend/zenddbi,davidl-zend/zenddbi,ollie314/server,ollie314/server,flynn1973/mariadb-aix,natsys/mariadb_10.2,flynn1973/mariadb-aix,natsys/mariadb_10.2,flynn1973/mariadb-aix,natsys/mariadb_10.2,natsys/mariadb_10.2,flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,ollie314/server,flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,flynn1973/mariadb-aix,ollie314/server,davidl-zend/zenddbi,ollie314/server,ollie314/server,flynn1973/mariadb-aix,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,natsys/mariadb_10.2,davidl-zend/zenddbi,natsys/mariadb_10.2,flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,davidl-zend/zenddbi,flynn1973/mariadb-aix,ollie314/server,ollie314/server,ollie314/server,natsys/mariadb_10.2,slanterns/server,davidl-zend/zenddbi