The driver for this patch is SEH, which will add yet another function
name variant in each of these places in each front end.  While I could
adjust each language appropriately, it seems to me that it is a bit
cleaner to centralize this knowledge.

The next possibly objectionable point is including dwarf2.h in tree.h.
I went ahead and did this because in the past we had talked about using
the dwarf language enum in LTO.  I could see eliminating the hackish
language_string -> enum mapping that is done in dwarf2out.c as well.

Comments?  Objections?


r~