Move www/httpdirfs to sysutils/fusefs-httpdirfs

The reason for this is to make the HTTPDirFS port more consistent with the
rest of FUSE ports.

Also, update pkg-descr to avoid talking directly to the user and presenting
judgmental assessments about the performance of the software.

Reported by:	danfe

Fix build on GCC-based systems:

  src/main.c:47: error: 'for' loop initial declaration used outside C99 mode

Approved by:	portmgr (tier-2 blanket)

New port: www/httpdirfs: FUSE filesystem to mount HTTP directory listings, with
a permanent cache

Have you ever wanted to mount those HTTP directory listings as if it was a
partition? Look no further, this is your solution. HTTPDirFS stands for
Hyper Text Transfer Protocol Directory Filesystem.

The performance of the program is excellent. HTTP connections are reused
due to the use of curl-multi interface. The FUSE component runs in
multithreaded mode.

There is a permanent cache system which can cache all the file segments you
have downloaded, so you don't need to these segments again if you access
them later. This feature is triggered by the --cache flag. This makes this
filesystem much faster than rclone mount.

The support for Airsonic / Subsonic server has also been added. This allows
you to mount a remote music collection locally.

WWW: https://github.com/fangfufu/httpdirfs