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@11065 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/mac/textctrl.cpp

@@ -13,7 +13,7 @@
 #pragma implementation "textctrl.h"
 #endif
 
-#ifdef __UNIX__
+#ifdef __DARWIN__
   #include <sys/types.h>
   #include <sys/stat.h>
 #else
@@ -34,7 +34,7 @@
 
 #if defined(__BORLANDC__) && !defined(__WIN32__)
   #include <alloc.h>
-#elif !defined(__MWERKS__) && !defined(__GNUWIN32) && !defined(__WXMAC_X__)
+#elif !defined(__MWERKS__) && !defined(__GNUWIN32) && !defined(__DARWIN__)
   #include <malloc.h>
 #endif