[rfc] conditional 128-bit long double

[Andrew Cagney]

> The only thing that would be better is if gdb could look up long double
> in the debug info:

GDB needs to come up in a sane state without debug info - stripped 
executable or even:

$ gdb
(gdb) print (long double) 1 * 2

so you can't rely on debug info.

> but I have no idea if one could even think doing such a thing in gdb.
> I expect to *never* have to handle applications with mismatched types,
> as I'm planning to bump the libc version number before this is over.

Won't you also want to brand the executable and object file?  Without 
that it will be too wasy to link the wrong object file into the wrong 
executable.

GDB handles ABI variants with OSABI sniffers that key off the brand.

Andrew