doc/libav-merge: mention the skipped AVFrame crop fields usage commits

doc/libav-merge.txt

@@ -99,6 +99,11 @@ Stuff that didn't reach the codebase:
 - Read aac_adtstoasc extradata updates from packet side data on Matroska once mov and the bsf in question are fixed (See 13a211e632 and 5ef1959080)
 - new bitstream reader (see http://ffmpeg.org/pipermail/ffmpeg-devel/2017-April/209609.html)
 - use of the bsf instead of our parser for vp9 superframes (see fa1749dd34)
+- use of the new AVFrame crop fields in h264/hevc/theora (see https://ffmpeg.org/pipermail/ffmpeg-devel/2017-May/211239.html)
+  - a02ae1c683 hevcdec: export cropping information instead of handling it internally
+  - 4fded0480f h264dec: be more explicit in handling container cropping
+  - c3e84820d6 h264dec: export cropping information instead of handling it internally
+  - 1202b71269 theora: export cropping information instead of handling it internally
 
 Collateral damage that needs work locally:
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