- configure.ac: Add -lpthread only if acx_pthread_ok is yes. In cygwin, we use Windows' thread so that we don't need -lpthread.
- base/mutex.h: Define NOMINMAX before we include windows.h.
- glog/*.h: Make sure that dllimport doesn't appear in cygwin. Note that windows.h may define _WIN32 macro.
- utilities.h: Define OS_CYGWIN.


git-svn-id: https://google-glog.googlecode.com/svn/trunk@30 eb4d4688-79bd-11dd-afb4-1d65580434c0