cobol: Use _perform_line_pairs instead of injecting encoded label names.

cobol: Use _perform_line_pairs instead of injecting encoded label names.

The gcobol front end has been communicating with GDB-COBOL by encoding
information into labels that are injected into the assembly language
with ASM_EXPR nodes.  That behavior is, at best, questionable.

These changes replace the "proccall" and "procret" types of those labels
in favor of a static _perform_line_pairs table that contains the same
information and is accessible by GDB-COBOL by virtue of its known name.

That table allows GDB-COBOL to "NEXT over COBOL PERFORM" statements in a
way that is familiar to users who have used "NEXT over function call".

Eventually that information should find its way into the .debug_info
section, but at the present time I don't know how to do that on either
the compiler or debugger sides.

Most of these changes involve eliminating gg_insert_into_assembler calls
and replacing them with the perform_is_armed/perform_line_pairs logic.

Some COBOL variable initialization changes crept in here, as well.

gcc/cobol/ChangeLog:

	* genapi.cc (DEFAULT_LINE_NUMBER): Remove unused #define.
	(parser_statement_begin): Implement perform_is_armed logic.
	(initialize_variable_internal): Handle both real and int types in
	SHOW_PARSE tracing.
	(section_label): Comment a renumbered insert_nop() for gdb-cobol
	logic.
	(paragraph_label): Likewise.
	(leave_procedure): Eliminate call to gg_insert_into_assembler().
	(parser_enter_section): Renumber insert_nop().
	(parser_perform): Eliminate call to gg_insert_into_assembler().
	(parser_perform_times): Likewise.
	(internal_perform_through): Likewise.
	(internal_perform_through_times): Likewise.
	(parser_leave_file): Create the static _perform_line_pairs table.
	(parser_sleep): Renumber insert_nop().
	(parser_division): Remove calls to initialize_the_data().
	(parser_perform_start): New call to insert_nop().
	(parser_perform_conditional): Likewise.
	(perform_outofline_before_until): Expanded comment.
	(perform_outofline_after_until): Eliminate call to
	gg_insert_into_assembler().
	(perform_outofline_testafter_varying): Likewise.
	(perform_outofline_before_varying): Likewise.
	(perform_inline_testbefore_varying):  New call to insert_nop().
	(create_and_call): Change a comment.
	* gengen.cc (gg_create_goto_pair): Change characteristics of a
	label.
	* parse.y: Change how data are initialized.
	* parse_ante.h (field_type_update): Likewise.
	* symbols.cc (cbl_field_t::set_signable): Likewise.
	(cbl_field_t::encode): Likewise.
	* symbols.h (struct cbl_field_t): Likewise.
	* util.cc (symbol_field_type_update): Likewise.
	(cbl_field_t::encode_numeric): Likewise.

libgcobol/ChangeLog:

	* valconv.cc (__gg__string_to_numeric_edited): Explanatory comment.