Add -mgnu-asm; change -mdec-asm to generate DEC assembler

Add -mgnu-asm; change -mdec-asm to generate DEC assembler
        compatible output.

	* common/config/pdp11/pdp11-common.c (pdp11_handle_option): Handle
	-munit-asm, -mgnu-asm, -mdec-asm.
	* config/pdp11/pdp11-protos.h (pdp11_gen_int_label): New.
	(pdp11_output_labelref): New.
	(pdp11_output_def): New.
	(pdp11_output_addr_vec_elt): New.
	* config/pdp11/pdp11.c: Use tab between opcode and operands.  Use
	%# and %@ format codes.
	(pdp11_option_override): New.
	(TARGET_ASM_FILE_START_FILE_DIRECTIVE): Define.
	(pdp11_output_ident): New.
	(pdp11_asm_named_section): New.
	(pdp11_asm_init_sections): New.
	(pdp11_file_start): New.
	(pdp11_file_end): New.
	(output_ascii): Use .ascii/.asciz for -mdec-asm.
	(pdp11_asm_print_operand): Update %# and %$ for -mdec-asm.  Add
	%o, like %c but octal.
	(pdp11_option_override): New.
	* config/pdp11/pdp11.h (TEXT_SECTION_ASM_OP): Update for
	-mdec-asm.
	(DATA_SECTION_ASM_OP): Ditto.
	(READONLY_DATA_SECTION_ASM_OP): New.
	(IS_ASM_LOGICAL_LINE_SEPARATOR): New.
	(ASM_GENERATE_INTERNAL_LABEL): Use new function.
	(ASM_OUTPUT_LABELREF): Ditto.
	(ASM_OUTPUT_DEF): Ditto.
	(ASM_OUTPUT_EXTERNAL): New.
	(ASM_OUTPUT_SOURCE_FILENAME): New.
	(ASM_OUTPUT_ADDR_VEC_ELT): Use new function.
	(ASM_OUTPUT_SKIP): Update for -mdec-asm.
	* config/pdp11/pdp11.md: Use tab between opcode and operands.  Use
	%# and %@ format codes.
	* config/pdp11/pdp11.opt (mgnu-asm): New.
	(mdec-asm): Conflicts with -mgnu-asm and -munix-asm.
	(munix-asm): Conflicts with -mdec-asm and -mgnu-asm.
	* doc/invoke.txt (PDP-11 Options): Add -mgnu-asm.

From-SVN: r262289