[Bug target/92055] [avr] Support 64-bit double

[gjl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92055

--- Comment #4 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
Created attachment 47114
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47114&action=edit
double64-5.diff: Support --with-double={32|64} --with-long-double={32|64}