TR 24731-2 (dynamic allocation functions) as API source

[Paul Eggert]

Joseph Myers wrote:
> (There was at least one instance of demand for TS 18661-1 roundeven:

While we're listing APIs glibc should have, I'll mention the NetBSD-inspired API 
for thread-safe access to time zone data, consisting of the new type timezone_t 
and the new functions tzalloc, tzfree, localtime_rz, and mktime_z, all declared 
in <time.h>. GNU Emacs and some other GNU apps use this API, and fall back on a 
Gnulib substitute when the system's C library lacks support, but the Gnulib 
substitute is slow and not thread-safe and this really needs to be done inside 
glibc.