* toffset.c: Added new file which implements the abstract interfaces

* toffset.c: Added new file which implements the abstract interfaces
	for manipulating the time offset fields in the os context.

ustime.c (krb5_us_timeofday): Add support for using the time offset
	fields in the os context.

timeofday.c (krb5_timeofday): Add support for using the time offset
	fields in the os context.

init_os_ctx.c (krb5_os_init_context): Initialize the time offset and
	flags fields in the os context.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@6647 dc483132-0cff-0310-8789-dd5450dbe970