The sproadic_*() macros have become unwieldy. This patch
replaces those convenience macros for global, clustered,
and partitioned scheduling. A part of this API change
is the explicit use of nanosecond time-values. Prior APIs
have used lt_t (litmus time), which had an implied time
scale of nanoseconds.

/bin apps and test suite also updated to use revised API.
Modifications to the test suite are mostly centered around
using nanoseconds instead of milliseconds.

Also add the priority parameter, which was missing.

Updated APIs to support arbitrary deadlines. Added macros for implicit
deadlines.

Note: Had to tweak Makefile to support gcc version >= 4.6 (moved -lrt to the
end of the link command).