to 2.4.0, as it has appeared in the 2.4.0-rc7 first time.
Being exported, AT_CLKTCK is returned by sysconf(_SC_CLK_TCK),
glibc falls back to the hard-coded CLK_TCK value when aux entry
is not present.
Glibc versions prior to 2.2.1 always use hard-coded CLK_TCK value.
For older applications/libc's which depends on hard-coded CLK_TCK
value user should set compat.linux.osrelease less than 2.4.0.
Approved by: kib (mentor)