* configure.in (auxdir): Replace by ...
	(toprel): ... new variable.
	(toplevel_srcdir): Construct from $toprel.
	* acinclude.m4 (GLIBCPP_ENABLE_THREADS): Use $toprel
	rather than .. to locate gcc source directory.
	(GLIBCPP_CONFIGURE): Replace $auxdir with $srcdir/$toprel.
	* aclocal.m4, configure: Rebuilt.

From-SVN: r43364