time: Allow later version licensing.
The FSF's Licensing and Compliance Lab noted a discrepancy in the
licensing of several files in the glibc package.
When timespect_get.c was impelemented the license did not include
the standard ", or (at your option) any later version." text.
Change the license in timespec_get.c and all copied files to match
the expected license.
This change was previously approved in principle by the FSF in
RT ticket #
1316403. And a similar instance was fixed in
commit
46703efa02f6ddebce5ee54c92f7c32598de0de6.