(expand_binop): New variable next_methods; pass to most recursive calls when trying to avoid libcalls.

(expand_binop): New variable next_methods; pass to most recursive calls when
trying to avoid libcalls.
Always check for a return value of zero in recursive calls.
(expand_float): Ensure TARGET has proper mode.
Pass OPTAB_LIB_WIDEN to expand_binop calls.

From-SVN: r7526