make vendors x86-specific. Part of issue #348
avoid instantiating function type with native by value in static horner. Fix #383
make extension tags extensible, fix #348
add protection in x86 detect
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.
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.
Fixed bogus assertion failures in fill_with_real_data() and fill_with_imag_data() reproducible_random_data_provider member functions.
Fixed compilation with BOOST_NO_EXCEPTIONS.
Updated with the latest timing code changes.
Added timing code overhead information printing.
OSX/Clang: (quick)fixed assertion failures.
Fixed BOOST_NO_EXCEPTIONS builds.
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).
Fixed an assert.
Fixed checked STL assertion failures.
Added an implementation note.
Fixed a few typos.
Fixed a bug in the reproducible_random_data_provider::randomize() member function.
Added more documentation notes.
Minor CT optimization.
Added "beta"/"prototype" support for GCC's bultin vector type.
Added a workaround for a GCC performance bug related to bultin_unreachable.
Minor other reafactoring and stylistic changes.