Factorize some constant related type computation
Fix #601 - Make enumerate works with pack
adding fast math macros in exponential log functions
Implements the raw_rec function

Returns the fastest yet least precise approximation of 1/x.
[#596] Refactorize fast_rec to use raw_rec + Newton Raphson everywhere
More fix in SSE4.1 insert
meaningfull unit tests for lookup
Fix #605 - Typo in tocomplex
make x86-specific tools still build fine on non-x86 architectures
re-indent sse2 multiplies, replace | by _mm_or_si128, and remove unnecessary bitwise_cast
remove unnecessary includes in scalar log10
remove bad casts in avx all_reduce, fix #607
Fix #606 correcting documentation of normcdf (2 typos exp in place of norm)
fix #605, bad result_type in tocomplex
cannot use sizeof in ALIGN_ON in stack_buffer, using 1 for now
Quick-fix for failed gather_includes builds when cross compiling (missing exceptions support).
Applied the same quick-fix to move_reuse and postconfigure as for gather_includes.
(note to nt2 devs: there seems to be duplication between the CMakeLists.txt files for the three tools)
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.
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.
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).