Implemented proper x86_64 signal handling. Have just one sigalrm handler.
Fix error() to not mysteriously give different output on stderr compared
to boot.log. Very basic stuff works now (freedos dir/exitemu).


git-svn-id: https://dosemu.svn.sourceforge.net/svnroot/dosemu/trunk@1601 7758b857-130e-0410-ab9c-d8735a528d18