Log Message:
sfeed: Update to 0.9.17

Changes:
0.9.17
------
 - Fallback author to feedname instead of unknown in sfeed_mbox.
 - Remove prefix in Subject: for sfeed_mbox to save some space.
   Filtering or custom labels can be made using the X-Feedname: header.
 - Document exit status in man pages.
 - Use a <pre> section per feed in sfeed_html/sfeed_frames.
 - Optimize UTF-8 decoding and column position calculation in sfeed_plain.