and similarly for long double, float. Those are from from
src/c++17/floating_from_chars.cc and only defined if
_GLIBCXX_HAVE_USELOCALE, i.e. depend on the XPG7 addition. Given that
only Solaris 11.4 supports XPG7, I've taken the 11.3 baselines to avoid
having separate ones for 11.3 and 11.4.
Tested on i386-pc-solaris2.11 and sparc-sun-solaris2.11 (sparc and x86,
32 and 64-bit, 11.3 and 11.4).