cygwin: select: use UNICODE console functions

cygwin: select: use UNICODE console functions

For historical reasons peek_console was calling the functions
PeekConsoleInputA and ReadConsoleInputA.  However, these functions are
not working correctly under at least codepage 65001 (UTF-8) on systems
prior to Windows 10.

Use PeekConsoleInputW and ReadConsoleInputW instead, which work
correctly under all systems and all codepages.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>