Use Win32 ::CommandLineToArgvW() to tokenize command line

Use the standard function in Unicode build instead of our own emulation, it
should give better results and is marginally more efficient as it does fewer
heap allocations than our own wxCmdLineParser::ConvertStringToArgs().

src/msw/main.cpp

@@ -29,7 +29,10 @@
     #include "wx/utils.h"
 #endif //WX_PRECOMP
 
-#include "wx/cmdline.h"
+// wxCmdLineParser is only used when we can't use ::CommandLineToArgvW().
+#if !wxUSE_UNICODE
+    #include "wx/cmdline.h"
+#endif
 #include "wx/dynlib.h"
 
 #include "wx/msw/private.h"
@@ -203,6 +206,22 @@ struct wxMSWCommandLineArguments
     wxMSWCommandLineArguments() { argc = 0; argv = NULL; }
 
     // Initialize this object from the current process command line.
+    //
+    // In Unicode build prefer to use the standard function for tokenizing the
+    // command line, but we can't use it with narrow strings, so use our own
+    // approximation instead then.
+#if wxUSE_UNICODE
+    void Init()
+    {
+        argv = ::CommandLineToArgvW(::GetCommandLineW(), &argc);
+    }
+
+    ~wxMSWCommandLineArguments()
+    {
+        if ( argc )
+            ::LocalFree(argv);
+    }
+#else // !wxUSE_UNICODE
     void Init()
     {
         // Get the command line.
@@ -239,6 +258,7 @@ struct wxMSWCommandLineArguments
         wxDELETEA(argv);
         argc = 0;
     }
+#endif // wxUSE_UNICODE/!wxUSE_UNICODE
 
     int argc;
     wxChar **argv;