An extflonum is like a flonum, but with 80-bit precision and
not a number in the sense of `number?': only operations such as
`extfl+' work on extflonums, and only on platforms where extflonums
can be implemented by hardware without interefering with flonums
(i.e., on platforms where SSE instructions are used for
double-precision floats).
[Patch provided by Michael Filonenko and revised by Matthew.]
The compiler tracks information about bindings that are known to
hold extflonums, but the JIT does not yet exploit this information
to unbox them (except as intermediate results).
The main change is to use C99 flexible array declarations
in structs, instead of declaring single-element arrays.
There are still a few -Wtautological-compare warnings
in 3m due to marco expansion.
and also changed vector, string, and byte string counts to
`intptr_t' instead of `int'.
Except for the vector count, etc. change, this is not really a
change for any currently supported platform, where `intptr_t'
is the same as `long'. It's a step to suporting Win64, though,
where `long' is the same as `int' instead of `intptr_t'.
