"setparams" command to update positional parameters.

	"setparams" command to update positional parameters.

	* tests/grub_script_setparams.in: New test.
	* Makefile.util.def: Rules for new test.

	* grub-core/script/argv.c (grub_script_argv_make): New function.
	* grub-core/script/execute.c (replace_scope): New function.
	(grub_script_setparams): New function.
	* grub-core/script/lexer.c: Remove unused variables.
	* grub-core/script/main.c: Register/unregister setparams command.
	* include/grub/script_sh.h (grub_script_argv_make): New prototype.
	(grub_script_setparams): New prototype.