ACPIhalt: Add more ACPI opcodes.

ACPIhalt: Add more ACPI opcodes.

	The AML parser implements only a small subset of possible AML
	opcodes. On the Fujitsu Lifebook E744 this and another bug in
	the parser (incorrect handling of TermArg data types) would lead
	to the laptop not turning off (_S5 not found).

	* grub-core/commands/acpihalt.c: Support OpAlias in the AML parser;
	in skip_ext_op(), handle some Type2Opcodes more correctly (TermArgs
	aren't always simply strings!); Add function to skip TermArgs
	* include/grub/acpi.h: Add new opcodes