Initial support for MRI style labels and expressions.

	Initial support for MRI style labels and expressions.
	* as.h (flag_mri): Declare/define.
	* as.c (show_usage): Mention -M and its synonym --mri.
	(parse_args): Add 'M' to std_shortopts.  Add "mri" to
	std_longopts.  Set flag_mri if -M is seen.
	(main): Call parse_args before input_scrub_begin.  Call
	expr_begin.
	* app.c (do_scrub_begin): Don't set lex for '"' or '\'' in MRI
	mode.  Do set lex for ';', '*', and '!' in MRI mode.
	(do_scrub_next_char): Remove MRI ifdef in LEX_IS_WHITESPACE case.
	In MRI mode, keep spaces between labels and colons.  Remove MRI
	ifndef around LEX_IS_ONECHAR_QUOTE case.  In MRI mode, don't use
	'!' or '*' as comment characters even if they are in
	comment_chars.
	* read.h (lex_type): No longer const.
	* read.c: Include libiberty.h.
	(lex_type): No longer const.
	(read_begin): In MRI mode, set lex_type of '?' to 3.
	(potable): Add dc, dc.b, dc.d, dc.l, dc.s, dc.w, dc.x, ds, ds.b,
	ds.l, ds.w, and xdef.
	(read_a_source_file): Change LABELS_WITHOUT_COLON ifdef to check
	for MRI mode at runtime rather than compile time.  Handle the EQU
	pseudo-op in MRI mode.  Remove bogus MRI ifdef around done_pseudo.
	Change NO_PSEUDO_DOT ifdef to also take effect for MRI mode at
	runtime.
	(cons): In MRI mode, always call parse_mri_cons rather than
	TC_PARSE_CONS_EXPRESSION.
	(parse_mri_cons): Always compile, not just when MRI is defined.
	Call TC_PARSE_CONS_EXPRESSION, not expression, when the input is
	not a string constant.  Handle A and E modifiers.
	(float_cons): Accept :xxxx, where the x's are hex digits.
	* expr.h (operatorT): Add O_eq, O_ne, O_lt, O_le, O_ge, O_gt.
	(expr_begin): Declare.
	* expr.c (integer_constant): In MRI mode, if the base was not
	specified, look for a suffix on the number to set the base.
	(mri_char_constant): New static function.
	(operand): Remove MRI ifdef.  In MRI mode, do various things: Pass
	0 as the base when calling integer_constant if there was no
	prefix.  Check for a hex constant suffix if when a leading '0' is
	seen.  Don't accept 0x or 0b as a prefix.  Check for E'chars' and
	A'chars'.  Handle MRI character constants.  Treat '"' as the
	unary bitwise not operator.  Treat $ as the program counter, or as
	the prefix for a hex constant.  Treat % as the prefix for a binary
	constant and @ as the prefix for an octal constant.  Treat : as
	the prefix for a hex constant.
	(op_encoding): Set '"' to O_bit_not, '<' to O_lt, and '>' to O_gt.
	(op_rank): No longer const.  Change rank values.
	(expr_begin): New function.
	(operator): New static function.
	(expr): Use operator.  Don't bother to mention the operator in
	warnings.  Remove bogus #if 0 code.  Handle new operatorT values.
	* atof-generic.c (atof_generic): In MRI mode, accept underscores
	around the exponent in floating point numbers.
	* symbols.h (symbols_case_sensitive): Declare.
	* symbols.c (symbols_case_sensitive): New global variable.
	(symbol_create): Check symbols_case_sensitive.
	(symbol_find_base): Likewise.
	(resolve_symbol_value): Handle new operatorT values.
	(print_expr_1): Likewise.
	(S_IS_LOCAL): In MRI mode, names beginning with two '?' characters
	are local.