The new routines convert back and forth between private type OS_Time and
a long integer which can be used in package Ada.Calendar.Conversions
routines to convert to Ada.Calendar.Time.

2019-08-19  Dmitriy Anisimkov  <anisimko@adacore.com>

gcc/ada/

	* libgnat/s-os_lib.ads, libgnat/s-os_lib.adb (To_Ada, To_C): New
	routines.

From-SVN: r274661