modified configure to allow configuration of wxMotif under Darwin/Mac OS X

wxWindows can be configured as wxMac or wxMotif under Mac OS X
replaced __WXMAC_X__ define by __DARWIN__ (general Darwin related issues)
moved dlopen/dlerror code to dynlib.cpp to make it available for wxMotif


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@11061 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/ctrlsub.h

@@ -86,8 +86,8 @@ public:
     int Number() const { return GetCount(); }
 #endif // WXWIN_COMPATIBILITY_2_2
 
-#ifdef __WXMAC_X__
-    virtual ~wxItemContainer() {}  // Added min for Mac X
+#ifdef __DARWIN__
+    virtual ~wxItemContainer() { }
 #endif
 
 protected: