Add testcase for admission of suspended tasks

The kernel needs to be able to deal with tasks that do not make
themselves a real-time task, but get configured by some other task
instead.
Add a test for admission of tasks that are currently running

Complements the prior test for suspended tasks. All plugins currently
pass this test.
User large enough buffer to read /proc/litmus/release_master

The string 'NO_CPU' needs to fit into the buffer.
Port Makefile to new Linux kernel header layout

The userspace versions of unistd.h have moved to include/uapi/asm in
recent kernel versions; we need to adjust the liblitmus Makefile
accordingly.

Further, on x86, the unistd_32.h and unistd_64.h files are now
actually being auto-generated; this also forced adjustments.

This patch is required for liblitmus to compile against Linux 3.10.
Switch NP flag format back to 32 bits (uint32_t)

This matches the corresponding change in the kernel.