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/dialog.h

@@ -22,8 +22,8 @@
 class WXDLLEXPORT wxDialogBase : public wxPanel
 {
 public:
-#ifdef __WXMAC_X__
-    ~wxDialogBase() {}  // Added min for Mac X
+#ifdef __DARWIN__
+    ~wxDialogBase() { }
 #endif
     // the modal dialogs have a return code - usually the id of the last
     // pressed button