[Bug fortran/82143] add a -fdefault-real-16 flag

[sch...@linux-m68k.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82143

--- Comment #21 from Andreas Schwab <sch...@linux-m68k.org> ---
The promotion_4.f90 test fails due to bad assumptions:

(gdb) whatis d
type = real(kind=10)