* ldgram.y (YYDEBUG): If not defined, define as 1.

	* ldgram.y (YYDEBUG): If not defined, define as 1.
	(CASE, EXTERN, START): New tokens.
	(mri_script_command): Handle CASE, EXTERN, INCLUDE, START.
	(casesymlist): New nonterminal.
	(extern_name_list): New nonterminal.
	* ldlex.l: Accept lower case trailing base specifiers.  Don't
	ignore the first digit when the base is a suffix.  Accept many
	EXPRESSION state tokens in MRI state.  Support MRI continuation
	lines and MRI semicolon comments.  Accept all MRI keywords in
	lower case.  Add CASE, EXTERN, and START MRI keywords.