Ada character types : tree code and DW_AT_encoding

[Paul Brook]

> A possible way to solve this problem is to add a single-bit flag to
> INTEGER_TYPE nodes that indicates whether this is actually a character
> type.  Then dwarf2out.c could just check the flag to determine what
> debug info to emit.  It looks like we have a number of flag bits that
> aren't being used in type nodes.  This is much better than trying to do
> string matches against type names to determine what is a character type.

We already have TYPE_STRING_FLAG used on array types. Maybe it would it make 
sense to use that?

Paul