x11-wm/sawfish: do not rebootstrap, install missing files

• Drop `autoreconf' from USES added in commit 246008f171263 for development version 1.12.90 which apparently required it, current stable version comes properly bootstrapped
• Fix the tar(1) command so all theme files are installed regardless of version thereof (bsdtar 3.5.1 traditionally defaults to /dev/sa0 while versions 3.6.x write to stdout which probably makes more sense nowadays)
• Assume maintainership for the time being, pet portlint(1)