some cleanup, remove some commented codes
simplify logics in filter tests, remove redundant code in arithm tests
add copyrights
remove interpolation.hpp
further simplify the logics in filter tests
use clean EXPECT_MAT_NEAR (no string output)
fix warnings, unify test names
fix the warnings in fft tests
Merge pull request #871 from bitwangyaoyao:2.4_acry