remove gengtype support for param_is use_param, if_marked and splay tree allocators

remove gengtype support for param_is use_param, if_marked and splay tree allocators

gcc/

	* plugin.c, plugin.def, ggc.h, ggc-common.c, gengtype.h, gengtype.c,
	gengtype-state.c, gengtype-parse.c, gentype-lex.l, gcc-plugin.h,
	doc/plugins.texi, doc/gty.texi: Remove support for if_marked and
	param_is.

include/

	* hashtab.h, splay-tree.h: Remove GTY markers.

From-SVN: r218558