Add KFR_STD_COMPLEX cmake option, fix std::complex issue

Merge pull request kfrlib#85 from acxz/archlinux_package

Add instructions for archlinux package

KFR 4.1

Changelog

make fp_precision_limit inline

Update README and CHANGELOG

Test iOS build in Xcode 10.1

short_fir: change default vector width

Update README.md

Tests for partition function