Add wxUSE_STD_CONTAINERS and turn it on by default.

Previously, wxUSE_STL enabled both implicit conversion of wxString to
std::[w]string and use of standard containers for the implementation of their
wx equivalents. Split up the two roles now by allowing to enable the use of
the standard containers independently of (backwards incompatible) implicit
conversion in wxString and actually enable wxUSE_STD_CONTAINERS by default.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67343 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/defs.h

@@ -89,6 +89,16 @@
        class 'bar'" */
 #   pragma warning(disable:4251)
 
+    /*
+        This is a similar warning which occurs when deriving from standard
+        containers. MSDN even mentions that it can be ignored in this case
+        (albeit only in debug build while the warning is the same in release
+        too and seems equally harmless).
+     */
+#if wxUSE_STD_CONTAINERS
+#   pragma warning(disable:4275)
+#endif /// wxUSE_STD_CONTAINERS
+
 #   ifdef __VISUALC5__
     /* For VC++ 5.0 for release mode, the warning 'C4702: unreachable code */
     /* is buggy, and occurs for code that does actually get executed */
@@ -2760,7 +2770,7 @@ typedef int (* LINKAGEMODE wxListIterateFunction)(void *current);
 #endif
 
 #if defined(__CYGWIN__) && defined(__WXMSW__)
-#   if wxUSE_STL || defined(wxUSE_STD_STRING)
+#   if wxUSE_STD_CONTAINERS || defined(wxUSE_STD_STRING)
          /*
             NASTY HACK because the gethostname in sys/unistd.h which the gnu
             stl includes and wx builds with by default clash with each other