[LOGONUI] Make Logon UI compilable again (#4684)

Logon UI was excluded from CMake build, probably for not being compliant
with 'warnings are errors' standard introduced at some point.
In the future, I would probably try to make Logon UI usable
alongside with the classic msgina interface.

- Add logonui back to CMakeLists
- Replace 'wcscpy_s' Vista+ function with StringCchCopyW
- Exclude some unused functions

Signed-off-by: Vitaly Orekhov <crce2000@mail.ru>
Reviewed-by: Stanislav Motylkov <x86corez@gmail.com>
Reviewed-by: Hermès Bélusca-Maïto <hermes.belusca-maito@reactos.org>

base/system/logonui/logonui.c

@@ -37,6 +37,7 @@ DrawLogoffScreen(HDC hdcMem)
     NT5_CreateLogoffScreen(L"Saving your settings...", hdcMem);
 }
 
+#if 0
 static ULONG
 GetULONG(LPWSTR String)
 {
@@ -81,6 +82,7 @@ GetULONG2(LPWSTR String1, LPWSTR String2, PINT i)
 
     return Value;
 }
+#endif
 
 static BOOL
 ParseCmdline(int argc, WCHAR* argv[])