reliable), now works in both sync and async modes
2. wxSafeYieldBug() corrected, wxWindowDisabler which is now used in it
added and documented
3. exec sample updated to illustrate capturing the subprocess output
4. wxStreamBase::IsOk() added
5. wxInputStream::Eof() added and non-blocking Eof() implementation in
wxPipeInputStream used by wxExecute
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@6400 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
