re PR c++/47301 ([C++0x] ICE: in fold_convert_loc, at fold-const.c:1906 with -fabi-version=1 and constexpr)

	PR c++/47301
	* decl.c (compute_array_index_type): Don't bother trying to deal
	with literal classes in ABI v1.

From-SVN: r171085