[m-rev.] for review: Use source file map to exclude default source file names.

[Julien Fischer]

On Tue, 14 Jan 2020, Peter Wang wrote:

> If a file name is listed in the source file map then
> do not use that file name as the source file for any other module.
> Fixes Mantis bug #489.
>
> compiler/source_file_map.m:
>    Make the source_file_map a bimap.
>
>    Make lookup_module_source_file return `no' if there is no source
>    file for the requested module, because the default file name for
>    that module has been mapped to another module.
>
> compiler/file_names.m:
>    Make module_name_to_file_name_general return a dummy file name
>    (that is not supposed to exist) when lookup_module_source_file
>    returns `no'.
>
> compiler/globals.m:
> compiler/introduce_parallelism.m:
> compiler/xml_documentation.m:
>    Conform to changes.

That's fine.

Julien.