* tree.h (PHI_CHAIN): New.
	* (tree-cfg.c, tree-dfa.c, tree-flow-inline.h, tree-into-ssa.c,
	tree-outof-ssa.c, tree-phinodes.c, tree-pretty-print.c,
	tree-ssa-alias.c, tree-ssa-ccp.c, tree-ssa-dom.c, tree-ssa-dse.c,
	tree-ssa-live.c, tree-ssa-loop.c, tree-ssa-phiopt.c, tree-ssa-pre.c,
	tree-ssa.c, tree-tailcall.c): Use PHI_CHAIN instead of TREE_CHAIN
	when traversing a list of PHI_NODEs.

From-SVN: r83273