sync: event - prototype futex-based event

git-svn-id: http://svn.boost.org/svn/boost/trunk@85809 b8fc166d-592f-0410-95f2-cb63ce0dd405
Corrected included headers to fix compilation problems on Solaris.

git-svn-id: http://svn.boost.org/svn/boost/trunk@85810 b8fc166d-592f-0410-95f2-cb63ce0dd405
Ported timed mutex for Windows. Changed time units to allow for non-system clocks. Minor fixes.

git-svn-id: http://svn.boost.org/svn/boost/trunk@85811 b8fc166d-592f-0410-95f2-cb63ce0dd405
Fixed compilation.

git-svn-id: http://svn.boost.org/svn/boost/trunk@85812 b8fc166d-592f-0410-95f2-cb63ce0dd405
Simplified the code a little.

git-svn-id: http://svn.boost.org/svn/boost/trunk@85814 b8fc166d-592f-0410-95f2-cb63ce0dd405