Added extended flag for navigation keys (Windows)

[klapovav]

This commit fixes a bug that occurs when simulating navigation keys in combination with Shift in Windows.

So far, it has not been possible to select text reliably using (Ctrl) + Shift + Navigation key. The result of this action was inconsistent and dependent on the state of the numlock. If numlock was on, Shift+RightArrow did not mark one letter, but moved the cursor. The reason for this is obvious from the sequence of keyboard messages that appear in the system queue.

The following code should cause 6 keyboard messages to appear in the Windows system message queue, but the system releases the Shift key while the navigation key is held down. If you are interested in the details, check out The effect of numLock & The effect of Shift

enigo.key_down(Key::LShift);
enigo.key_click(Key::RightArrow);
enigo.key_click(Key::RightArrow);
enigo.key_up(Key::LShift);

Message log from the low-level hook
Before:

Keyboard event | scan: (0x)00  | virtual: LShiftKey = (0x)A0     flags INJECTED
Keyboard event | scan: (0x)22A | virtual: LShiftKey = (0x)A0     flags        KEY_RELEASED      
Keyboard event | scan: (0x)00  | virtual:     Right = (0x)27     flags INJECTED
Keyboard event | scan: (0x)00  | virtual:     Right = (0x)27     flags        KEY_RELEASED
Keyboard event | scan: (0x)2A  | virtual: LShiftKey = (0x)A0     flags INJECTED       
Keyboard event | scan: (0x)22A | virtual: LShiftKey = (0x)A0     flags        KEY_RELEASED       
Keyboard event | scan: (0x)00  | virtual:     Right = (0x)27     flags INJECTED
Keyboard event | scan: (0x)00  | virtual:     Right = (0x)27     flags        KEY_RELEASED
Keyboard event | scan: (0x)2A  | virtual: LShiftKey = (0x)A0     flags INJECTED      
Keyboard event | scan: (0x)00  | virtual: LShiftKey = (0x)A0     flags INJECTED, KEY_RELEASED

After:

Keyboard event | scan: (0x)00 | virtual: LShiftKey = (0x)A0     flags INJECTED
Keyboard event | scan: (0x)00 | virtual:     Right = (0x)27     flags EXTENDEDKEY, INJECTED
Keyboard event | scan: (0x)00 | virtual:     Right = (0x)27     flags EXTENDEDKEY, INJECTED, KEY_RELEASED
Keyboard event | scan: (0x)00 | virtual:     Right = (0x)27     flags EXTENDEDKEY, INJECTED
Keyboard event | scan: (0x)00 | virtual:     Right = (0x)27     flags EXTENDEDKEY, INJECTED, KEY_RELEASED
Keyboard event | scan: (0x)00 | virtual: LShiftKey = (0x)A0     flags INJECTED, KEY_RELEASED

[pentamassiv]

Thank you very much for your PR. I will have a look at it within the next two weeks. Sorry about the delay

[pentamassiv]

Other than the above comments, the PR looks good and is ready to be merged.

[pentamassiv]

@klapovav I was unable to reproduce the issues you described. I am only using a VM to test Windows though so that might be why. For me the text consistently is marked before and after the change. Do you have an idea why or do you know of another way this issue can be observed?