Fixed and improved timing code:
 - reduced overhead and provided overhead estimates for more precise measurements
 - requires further cleanup and updating of affected code).
Updated and refactored the perform_benchmark() function template.

Conflicts:

	modules/unit/include/nt2/sdk/unit/perform_benchmark.hpp
Fixed/updated remaining code affected by the timing code changes.
Added attempts to prevent the compiler and/or the CPU from reordering and/or removing calls to timing functions.
Changed the default time unit to microseconds.
Added and used the priority_booster_t utility class.
Added more todo and implementation notes.

Conflicts:

	modules/unit/include/nt2/sdk/unit/perform_benchmark.hpp
OSX/Clang: (quick)fixed assertion failures.
Further improved stability/accuracy of the timing functions overhead (still not "perfect", especially for now()).
Optimized the median<>() function template and (temporarily) moved it into the now.cpp.
Switched to the rand48 PRNG (as it is faster) and (temporarily) moved the reusable PRNG functions into the now.cpp.
Minor other refactoring and stylistic changes.

Conflicts:

	modules/core/signal/bench/static_fft.cpp
Created a virtual interface class for benchmarks. Used it to make the perform_benchmark function a non template and (temporarily) moved it to now.cpp.
Used the perform_benchmark(_impl) function in now.cpp to accurately calculate the timing functions overhead (this now produces stable/reproducible results).
Fixed checked STL assertion failures.
Added an implementation note.
Fixed a few typos.
Added more documentation notes.
Added a todo note.
Introduce libnt2_unit

This patch provides a semi-compiled lirbary for handling NT2 unit
tests along with simplification of its dependencies and implementation.
Introduce libnt2_bench

This patch provides a semi-compiled benchmarking library that
streamlines the way we wrote benchmarks in NT2 and make benchmarks
definition simpler and more flexible.
Fix Documentation for test.unit
Fix unit tests with modified behavior due to header rearrangement
Various fixes for dynamic library mode for libnt2_unit
Improvement in benchmark interface
Small fix in ulp for integral under MSVC
Fix composite_reference test
More fixes for DYNLIB mdoe in benchmark
make test_suite and unit_test base classes visible
Fix test over of_size_