hints/hpux - only run d_strtold define override check on version < 11.23

I added a version check around the logic as the comment already says
that "In HP-UXes prior to 11.23 strtold() returned a HP-UX specific
union called long_double, not a C99 long double."

The logic did not check for the version mentioned in the comment, it
simply greped for something that is no longer present in the file:

    grep 'double strtold.const' /usr/include/stdlib.h

outputs nothing on HPUX version B.11.31.

But

    grep "double strtold" /usr/include/stdlib.h

outputs:

    extern long_double strtold __((const char * __restrict, char ** __restrict));
    extern long double strtold __((const char * __restrict, char ** __restrict));

on HPUX version B.11.31.

0 files changed, 0 insertions, 0 deletions