common.opt: Document --param.

common.opt: Document --param.

	* common.opt:  Document --param.
	* opts.c (columns, undocumented_msg): New.
	(print_help): Get number of columns from environment.  Print
	--param help.  Tweak newline handling.
	(print_param_help): New.
	(print_filtered_help): Better handling of duplicates.  Complain
	about undocumented switches.
	(print_switch): New.
	(wrap_help): Improve wrapping, use COLUMNS.
	* opts.sh: Ignore comments in records.
	* params.def: Fix typos and remove trailing periods.
	* toplev.c (display_help): Don't dump --param help.
	* doc/sourcebuild.texi: Update.
java:
	* lang.opt: Don't show -MD_ and -MDD_.

From-SVN: r69581