rsync-hfscomp: cleanup: review/fix implicit function declarations; note lack of upstream security updates

[mascguy (Christopher Nielsen)]

Minor cleanup items for this port, in the spirit of tidiness:

• Review/fix implicit function declarations;
• Amend notes to call out lack of upstream security updates

While the goal is to ultimately retire this port, in favor of patching the latest upstream release with the same functionality - tracked by issue:60792 - that will require a LOT of careful work. Including detailed review with both our folks, as well as upstream, before release. Ditto for pre-release testing, as it's critical that we don't break such an important piece of software. (Data loss due to buggy patches, is something we want to avoid at all costs.)

Nonetheless, for the near term, take care of cleanup items for this port.

[mascguy (Christopher Nielsen)]

Implicit declarations to fix:

  snprintf: found in rsync-3.1.2/config.log
  mkfifo: found in rsync-3.1.2/config.log
  strcmp: found in rsync-3.1.2/config.log
  unlink: found in rsync-3.1.2/config.log
  _exit: found in rsync-3.1.2/config.log
  strcpy: found in rsync-3.1.2/config.log
  mkstemp: found in rsync-3.1.2/config.log
  vsnprintf: found in rsync-3.1.2/config.log
  exit: found in rsync-3.1.2/config.log
  fork: found in rsync-3.1.2/config.log
  syscall: found in rsync-3.1.2/config.log

[Christopher Nielsen <mascguy@…>]

In 8a65fea3f3a636b079b4938f346110f982fb9a1a/macports-ports (master):

rsync-hfscomp: fix implicit declarations

• Also add security warning to notes, relative to daemon use

Fixes: #63737