Remove static (#90)

Remove static (#90)

Update ci.yml

Fix BOOST_MPL_AUX_ASSERT_NOT_NA

Fix BOOST_MPL_AUX_ASSERT_NOT_NA

Merge branch 'next-prior' of https://github.com/ecatmur/mpl into feat…

…ure/issue-69

Merge branch 'next-prior' of https://github.com/ecatmur/mpl into feat…

…ure/issue-69

Merge branch 'next-prior' of https://github.com/ecatmur/mpl into feat…

…ure/issue-69

Merge branch 'next-prior' of https://github.com/ecatmur/mpl into feat…

…ure/issue-69

Avoid `Wzero-as-null-pointer-constant` warning (#75)

Newer compilers may warn when using `0`, e.g.:
```
./boost/iterator/detail/facade_iterator_category.hpp:161:5: error: zero as null pointer constant [-Werror,-Wzero-as-null-pointer-constant]
    BOOST_MPL_ASSERT_NOT((is_iterator_category<Traversal>));
    ^
./boost/mpl/assert.hpp:324:58: note: expanded from macro 'BOOST_MPL_ASSERT_NOT'
              boost::mpl::assert_not_arg( (void (*) pred)0, 1 ) \
```