- fix bug: click on red close box in top-right corner would not quit the server

- fix bug: don't print '304' HTTP errors in the log pane: it only scares users and it just means that Mongoose reported the file as 'Not Modified' which is perfectly legal.
changed the MSVC2010 project to use the internal pthreads emulation, rather than the WinPthreads32 library. This is a temporary change until winpthreads is fixed.