adding check for syskeydown on control and alt

(cherry picked from commit d191a8b9f806641ba5ebdbfe059068dd15056124)

platform/windows/os_windows.cpp

@@ -1091,9 +1091,9 @@ LRESULT OS_Windows::WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 		case WM_KEYDOWN: {
 
 			if (wParam == VK_SHIFT)
-				shift_mem = uMsg == WM_KEYDOWN;
+				shift_mem = (uMsg == WM_KEYDOWN || uMsg == WM_SYSKEYDOWN);
 			if (wParam == VK_CONTROL)
-				control_mem = uMsg == WM_KEYDOWN;
+				control_mem = (uMsg == WM_KEYDOWN || uMsg == WM_SYSKEYDOWN);
 			if (wParam == VK_MENU) {
 				alt_mem = (uMsg == WM_KEYDOWN || uMsg == WM_SYSKEYDOWN);
 				if (lParam & (1 << 24))