invoke.texi: Document max-jump-thread-duplication-stmts PARAM.

	* doc/invoke.texi: Document max-jump-thread-duplication-stmts PARAM.
	* tree-ssa-dom.c: Include params.h.
	(thread_across_edge): If there are too many statements in the
	target block, then do not thread through it.
	* Makefile.in (tree-ssa-dom.o): Depend on $(PARAMS_H).
	* params.def (PARAM_MAX_JUMP_THREAD_DUPLICATION_STMTS): New PARAM.

From-SVN: r106503