filesystems/mtools: the port had been updated to version 4.0.49

- Correctly detect overlong file names, especially when
  multibyte (UTF-8) strings are concerned
- Fix off-by-one error in two calls to native_to_wchar()
- When changing disk label, ignore any plain file which
  would match the label
- Add missing newlines in error messages about disk geometry
- Do not print error message if getting geometry is simply
  not supported by device type (such as for loop devices)
- If full geometry of a device is not available (such as for
  loop devices), at least make use of the size

filesystems/mtools: update the port to the latest version 4.0.48

While here, adjust LICENSE (GPLv3 or later), respect PREFIX more,
wrap one very long line, and install useful documentation files.

filesystems/mtools: the port had been updated to version 4.0.47

While here, simplify one regular expression in the `post-patch'
target recipe, garbage-collect a patch, and sort the pkg-plist.

filesystems: add new category for file systems and related utilities

The filesystems category houses file systems and file system utilities.
It is added mainly to turn the sysutils/fusefs-* pseudo-category into
a proper one, but is also useful for the sundry of other file systems
related ports found in the tree.

Ports that seem like they belong there are moved to the new category.
Two ports, sysutils/fusefs-funionfs and sysutils/fusefs-fusepak are
not moved as they currently don't fetch and don't have TIMESTAMP set
in their distinfo, but that is required to be able to push a rename
of the port by the pre-receive hook.

Approved by:	portmgr (rene)
Reviewed by:	mat
Pull Request:	https://github.com/freebsd/freebsd-ports/pull/302
PR:		281988