Bump up filename and path limits to accommodate 255 Unicode character paths,
like Windows (UTF-8 encoded). (The maximum length of an encoded code point
is four bytes, so NAME_MAX / MAXNAMLEN becomes ~1020.) PATH_MAX is bumped by
a factor of four as well to accomodate longer names.
Some associated limits like _XOPEN_NAME_MAX, _XOPEN_PATH_MAX, FILENAME_MAX
Glob is modified to allocate now larger path buffers on the heap, rather
than the stack.
EXTATTR_MAXNAMELEN is de-linked from NAME_MAX; there's no obvious reason
attribute names need to be longer than 255 bytes. In particular, Windows
Alternate Data Stream names cannot be longer than 255 bytes.
The old 1024 byte path limit is retained as OLD_PATH_MAX. Several ABIs are
preserved by retaining the old limit.
Finally, UFS is modified to enforce its existing 255 byte name limit.