been around since 386BSD-0.1 import; they have been present in 4.4BSD-Lite
at least, can't currently check if even in 4.3BSD
put note aboud eventual removing of compatibility formats to NOTES, it's
hardly a bug description
Like Plauger's implementation in "The Standard C Library", we use strtod(),
which will limit the range of values that can be converter properly if
long double has greater precision or range than double.
We will need a string to long double function to handle this properly, but
this change is better than the previous behavior of ignoring the existance
of long doubles.