gruel: adding wrapper layer for gruel threads to enable setting thread affinity.

Working in Linux; programmed for Windows (but untested); nops for OSX.
core: working thread affinity concept into gr_blocks.

Example in gnuradio-core/src/examples/mp-sched/affinity_set.py

Documentation describing API in docs/doxygen/other/thread_affinity.dox
QA: adding a test to make sure the set_processor_affinity calls work and top_block starts correctly.
gruel: need to include windows.h to know about HANDLE.
sched: added documentation for affinity setting functions.
gruel: renamed mask to dword_mask
gruel: Added WIN32_LEAN_AND_MEAN definition before windows.h include
core: thread affinity example core set changed.

The affinity call will work if at least 1 of the specified cores is present. This fixes a problem if running on a single-core machine.
Merge branch 'master' of gnuradio.org:gnuradio
core: QA code import fix.

Prevents getting pmt module from the installed library.