* configure.in: Add new THREADCXXFLAGS variable.
  	Handle POSIX threads on alpha*-dec-osf*.
	* configure: Regenerate.
	* Makefile.am: Add THREADCXXFLAGS to AM_CXXFLAGS.
	* Makefile.in: Regenerate.

Co-Authored-By: Rainer Orth <ro@TechFak.Uni-Bielefeld.DE>

From-SVN: r69997