1. wxThread changes (detached/joinable) for MSW and docs updates

2. wxUSE_GUI=0 compilation for MSW (use vc6dll.t with tmake) and many small
   fixes related to this
3. an attempt to make wxLog more MT friendly
4. a small fix for wxRegConfig: it doesn't create empty unused keys any
   more (SetPath() would always create a key, now it's deleted if it was
   empty)


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@4712 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/regconf.cpp

@@ -160,13 +160,25 @@ void wxRegConfig::SetPath(const wxString& strPath)
   }
 
   // recombine path parts in one variable
-  wxString strRegPath;
+  wxString strOldPath = m_strPath, strRegPath;
   m_strPath.Empty();
   for ( size_t n = 0; n < aParts.Count(); n++ ) {
     strRegPath << '\\' << aParts[n];
     m_strPath << wxCONFIG_PATH_SEPARATOR << aParts[n];
   }
 
+  if ( m_strPath == strOldPath )
+      return;
+
+  // as we create the registry key when SetPath(key) is done, we can be left
+  // with plenty of empty keys if this was only done to try to read some value
+  // which, in fact, doesn't exist - to prevent this from happening we
+  // automatically delete the old key if it was empty
+  if ( m_keyLocal.IsEmpty() )
+  {
+      m_keyLocal.DeleteSelf();
+  }
+
   // change current key(s)
   m_keyLocal.SetName(m_keyLocalRoot, strRegPath);
   m_keyGlobal.SetName(m_keyGlobalRoot, strRegPath);