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/frame.h

@@ -58,8 +58,8 @@ class WXDLLEXPORT wxFrameBase : public wxWindow
 public:
     // construction
     wxFrameBase();
-#ifdef __WXMAC_X__
-    virtual ~wxFrameBase() {}  // Added min for Mac X
+#ifdef __DARWIN__
+    virtual ~wxFrameBase() { }
 #endif
 
     wxFrame *New(wxWindow *parent,