Add optional php-win.exe variation of the CLI sapi.

Add optional php-win.exe variation of the CLI sapi.
php-win.exe runs in the windows GUI subsystem, and thus
has no console; stdio handles are effectively set to /dev/null
and no "dos box" will appear on screen when running scripts
using this sapi (php-gtk people will be familiar with this concept).

Aside from those differences, php-win.exe is 100% identical to
regular CLI