Use SPECIAL_PERMS on MirBSD, too. Fix build.
Improve support for HTTPS master site URLs:
As the default fetch program "tnftp" (in "pkgsrc" and all released
versions of NetBSD) doesn't support HTTPS prefer "fetch" (DragonFlyBSD,
FreeBSD and Minix) or Curl (CygWin, Linux, Mac OS X, Solaris) if available.

Change during pkgsrc-freeze approved by Greg Troxel and Thomas Klausner.