re PR tree-optimization/51074 (No constant folding performed for VEC_PERM_EXPR, VEC_INTERLEAVE*EXPR, VEC_EXTRACT*EXPR)

	PR tree-optimization/51074
	* fold-const.c (vec_cst_ctor_to_array, fold_vec_perm): New functions.
	(fold_binary_loc): Handle VEC_EXTRACT_EVEN_EXPR,
	VEC_EXTRACT_ODD_EXPR, VEC_INTERLEAVE_HIGH_EXPR and
	VEC_INTERLEAVE_LOW_EXPR with VECTOR_CST or CONSTRUCTOR operands.
	(fold_ternary_loc): Handle VEC_PERM_EXPR with VECTOR_CST or
	CONSTRUCTOR operands.
	* tree-ssa-propagate.c (valid_gimple_rhs_p): Handle ternary
	expressions.
	* tree-vect-generic.c (lower_vec_perm): Mask sel_int elements
	to 0 .. 2 * elements - 1.

From-SVN: r181297