Don't `inline` popcount
Don't `inline` popcount

This makes no sense as we need `popcount()` to exist as external symbol. In fact this breaks with C99 compilers
which rightfully detect that `popcount` is not used at all, and therefore compile `popc.c` to an essentially empty  `popc.o` object... resulting in linker errors on GHC 7.0/7.2 when using such clever compilers...
bgamari/unordered-containers