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

[Richard Kenner]

    * When starting to parse a new source file do:
       linemap_add (&line_table, LC_ENTER, false, filename, 1);
    but if it's the first/main source file it's probably better to
    use LC_RENAME instead of LC_ENTER, since otherwise the code will
    think that filename is "included" from <built-in>.  (The compile
    server branch tries to do things a little differently, btw.)

Remember that Ada is not using the lexer, so these (and subsequent) calls
make no sense to me.  Can you look at the existing code and tell me what
has to be changed?