* source.c: Make global variables current_source_symtab and

    * source.c: Make global variables current_source_symtab and
        current_source_line static.
        (list_command): Moved to cli/cli-cmds.c.
        (ambiguous_line_spec): Moved to cli/cli-cmds.c.
        (get_first_line_listed): New accessor function.
        (get_lines_to_list): New accessor function.
        (get_current_source_symtab_and_line): New function. Retrieves the
        position in the source code that we consider current.
        (get_current_or_default_source_symtab_and_line): New function.
        Like the above but attempts to determine a default position if one
        is not currently defined.
        (set_current_source_symtab_and_line): New function. Sets the source
        code position considered current and returns the previously set one.
        (clear_current_source_symtab_and_line): Reset stored information about
        a current source line.
        (_initialize_source): Remove registration for the "list" command and
        its alias.
        * source.h: Add declarations for the new functions above.
        * symtab.h: Remove declarations for the global variables mentioned
        above.
        * breakpoint.c (parse_breakpoint_sals): Use accessor functions to
        obtain current source line.
        * linespec.c (decode_line_1): Ditto.
        * macroscope.c (default_macro_scope): Ditto.
        * scm-lang.c (scm_unpac): Ditto.
        * stack.c (print_frame_info_base): Ditto.
        * symfile.c (clear_symtab_users): Ditto.
        * symtab.c (decode_line_spec): Ditto.
        * cli/cli-cmds.c (list_command): Moved here from source.c.
        (ambiguous_line_spec): Moved here from source.c.
        (_init_cli_cmds): Add definition for "list" and its alias.
        * Makefile.in: Update dependencies.