uClibc can be built without fenv support, extend the configure check for
decimal floating point to probe the existance of fenv.h, too.

libgcc/ChangeLog:

2013-03-24  Bernhard Reutner-Fischer  <aldot@gcc.gnu.org>

	* configure.ac (libgcc_cv_dfp): Extend check to probe fenv.h
	availability.
	* configure: Regenerate

From-SVN: r204562