According to POSIX and both OSX and Linux manpages,
strcasecmp comes from strings.h, not string.h.

Most OSes also have them available in string.h,
but we just fixed the headers on Haiku and it now
only provides them in strings.h.

We might want to fall back to string.h for other
OSes though...

cf.
http://pubs.opengroup.org/onlinepubs/009695399/functions/strcasecmp.html
http://linux.die.net/man/3/strcasecmp
https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/strcasecmp.3.html

Reduce the number of unnecessary memmove() calls.

The null byte is whitespace, too.

Fixes build failure because assert.h was not included.

Remove the C list_head library and use type-safe C++ instead.

Provide the full API.