More musl.

Removes (or adds new) our old manual handwritten implementations for the following functions:

  bsearch, atoi, atol, atoll, qsort, bcmp, bzero, bcopy, strspn, strcspn, stpcpy, strncat, memchr, strnlen, strstr, strchr, strrchr, index, rindex, strdup, strndup, strpbrk, strtok, strtok_r.

Putting this up for looks already, some tests fail, so not yet ready for merge.