don't use mbstowcs(NULL) with Cygwin (closes #10526)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@59208 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/ole/oleutils.cpp

@@ -133,9 +133,10 @@ wxBasicString::wxBasicString(const wxString& str)
 // Takes an ANSI string and transforms it to Unicode
 void wxBasicString::Init(const char *sz)
 {
-    // get the size of required buffer
+    // get the size of required buffer: MetroWerks and Cygwin crash if NULL is
+    // passed to mbstowcs()
     UINT lenAnsi = strlen(sz);
-#ifdef __MWERKS__
+#if defined(__MWERKS__) || defined(__CYGWIN__)
     UINT lenWide = lenAnsi * 2 ;
 #else
     UINT lenWide = mbstowcs(NULL, sz, lenAnsi);