Changelog: explicit that xBR scaler is implemented as a filter
avfilter/xbr: consistent use of @see
avfilter/xbr: fix TODO entry
avfilter/xbr: fix filter description field
avfilter/xbr: drop yet another x2 reference
doc/filters: explicit and complete xBR documentation
Merge remote-tracking branch 'github/master'

* github/master:
  tests: Fix test name for pixfmts tests

Merged-by: Michael Niedermayer <michaelni@gmx.at>