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.

The -f option required manually *also* setting
the -w option. This is no longer required.

While at it, simplify the code by using the /proc interface.

Add a wrapper for /proc/litmus/stats to make it easy to query the
number of tasks already waiting for a task set release.