re PR c++/55337 (ICE tree check: expected sizeof_expr, have alignof_expr in cp_tree_equal, at cp/tree.c:2608)

	PR c++/55337
	* tree.c (cp_tree_equal) <case ALIGNOF_EXPR>: Use SIZEOF_EXPR_TYPE_P
	only on SIZEOF_EXPR.

	* g++.dg/template/alignof2.C: New test.

From-SVN: r193558