Define wxDEBUG_LEVEL in both debug and release builds as 1.

By default include assertions and debug logging in both debug and release
builds but disable them in application release builds (when NDEBUG is
defined).

Also update (more accurately, replace) debugging overview.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61886 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/log.h

@@ -1573,5 +1573,14 @@ wxSafeShowMessage(const wxString& title, const wxString& text);
     #undef WX_WATCOM_ONLY_CODE
 #endif
 
+// macro which disables debug logging in release builds: this is done by
+// default by IMPLEMENT_APP() so usually it doesn't need to be used explicitly
+#ifdef NDEBUG
+    #define wxDISABLE_DEBUG_LOGGING_IN_RELEASE_BUILD() \
+        wxLog::SetLogLevel(wxLOG_Info)
+#else // !NDEBUG
+    #define wxDISABLE_DEBUG_LOGGING_IN_RELEASE_BUILD()
+#endif // NDEBUG/!NDEBUG
+
 #endif  // _WX_LOG_H_