using _mm256_castsi128_si256 instead of _mm256_insertf128_si256 in shift_left/shift_right to avoid uninitialized warning
re-organizing vector_of to ensure the various specializations are not ambiguous
Roll helpers doesn't need to use nt2::abs for abs on double
Fix Issue #453

Whenever NT2_TEST_CASE_TPL or NT2_TEST_CASE_TPL_MPL is called and
their respective types sequence or lists is empty, the corresponding
test is skipped and an informative message is displayed.
factoring reduction code for trig functions
adding two trigonometric constants
scalar all must be defined on bool and return a bool
using the new constants in trig reductions
bad comment in deginrad
constant 1/90
using the constants in reduce functions
merging fand d trig_reduction.hpp
 factorizing double simd/scalar trig reduction