Ada, treelang needs to be converted to --enable-mapped-location

[Richard Kenner]

    When I look at the Ada front-end it looks straight-forward too.  I can
    sketch out what is needed and/or provide advice, but I think it is
    best the respective front-end maintainers make and test the actual
    changes.

Indeed the sketch would help.

    The basic constraint is you cannot set filename or line independently
    in input_location, DECL_SOURCE_LOCATION, or EXPR_LOCATION, but must
    get them from the line_table.  And it recommended that you "allocate"
    the source_location integers during initial lexing.  Note you can
    optionally also remember column numbers of declarations and
    expressions. 

Note that Ada uses it own lexer and does the inverse operation:
setting "input_location" to the values it obtained in its scan.  With
the exception of that code, every other place does what you mention.

So indeed I suspect the changes are tiny, but would appreciate a little more
details about what needs to be done.