Support DEFPARAMENUM in params.def

Support DEFPARAMENUM in params.def

2015-10-13  Tom de Vries  <tom@codesourcery.com>

	* Makefile.in (PARAMS_H, PLUGIN_HEADERS): Add params-enum.h.
	* params-enum.h: New file.
	* opts.c (handle_param): Handle case that param arg is a string.
	* params-list.h: Handle DEFPARAMENUM5 in params.def.
	* params.c (find_param): New function, factored out of ...
	(set_param_value): ... here.
	(param_string_value_p): New function.
	* params.h (struct param_info): Add value_names field.
	(find_param, param_string_value_p): Declare.

From-SVN: r228755