issue-549: handle most recent mingw that has sleep and nanosleep

I.e. we have to check their presence in configure and in case of their
presence we have to avoid re-defining then in window's port.h



git-svn-id: http://gperftools.googlecode.com/svn/trunk@223 6b5cf1ce-ec42-a296-1ba9-69fdba395a50
issue-546: fixed return type of Release_AtomicExchange on arm6+



git-svn-id: http://gperftools.googlecode.com/svn/trunk@224 6b5cf1ce-ec42-a296-1ba9-69fdba395a50
bump version number for 2.1rc



git-svn-id: http://gperftools.googlecode.com/svn/trunk@225 6b5cf1ce-ec42-a296-1ba9-69fdba395a50
updated NEWS and packages/ for 2.1rc



git-svn-id: http://gperftools.googlecode.com/svn/trunk@226 6b5cf1ce-ec42-a296-1ba9-69fdba395a50