This patch makes it so that if a user provides a groupname/username
instead of an id, chown will automatically convert it to a gid/uid
using getgrnam() or getpwnam() respectively.
This was a workaround to be able to build on case-insensitive file
systems where it might get confused about <string.h> vs <String.h>.
Let's just not support building that way, so String.h can have an
objectively nicer name. :^)
