The SIG_BUDGET should be ignored until the user
code is ready for them, even if that code has
already set up a signal handler.

This updates create_rt_task() to take an rt_task parameter
instead of a number of task parameters.  This probably
should have been a part of patches recent patches that revised
the sproadic_*() macros.

Conflicts:
	bin/base_mt_task.c
	bin/rt_launch.c
	bin/rtspin.c
	include/litmus.h
	src/litmus.c
	src/task.c

Conflicts:
	Makefile
	bin/rt_launch.c
	bin/rtspin.c
	src/task.c

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.

Adds init_rt_task_param(). Facilitates setting up default
real-time task attributes that cannot be set by memset(0).

This patch adds cluster scheduling options to
rtspin and rt_launch. The convenience routines
in litmus.h were also updated to facilitate
clustered scheduling. For partitioned scheduling,
just set cluster_size = 1 (default size for rtspin
and rt_launch).