libav: update libav from v9.6 to v9.8

version 9.8:
- kmvc: Clip pixel position to valid range
- kmvc: Use fixed sized arrays in the context
- indeo: Reject negative array indexes
- indeo: Check for reference when inheriting motion vectors
- indeo: Properly forward the error codes
- mjpeg: Check the unescaped size for overflows
- wmapro: Error out on impossible scale factor offsets
- wmapro: Check the min_samples_per_subframe
- wmapro: Return early on unsupported condition
- wmapro: Check num_vec_coeffs against the actual available buffer
- wmapro: Make sure there is room to store the current packet
- lavc: Move put_bits_left in put_bits.h
- 4xm: Do not overread the source buffer in decode_p_block
- 4xm: Check bitstream_size boundary before using it

version 9.7:

Most of the following fixes resulted from test samples that the Google
Security Team has kindly made available to us:

- 4xm: fix several programming errors to avoid crashes, etc.
- apetag: use int64_t for filesize
- jpegls: Fix invalid writes to memory
- ljpeg: use the correct number of components in YUV
- mjpeg: Validate sampling factors
- mjpegdec: properly report unsupported disabled features
- mjpegdec: validate parameters in mjpeg_decode_scan_progressive_ac
- mpegvideo: allocate sufficiently large scratch buffer for interlaced vid
- pixdesc: mark gray8 as pseudopal
- smacker: fix several programming errors to avoid crashes, etc.
- tiff: do not overread the source buffer
- vmd: drop incomplete chunks and spurious samples
- vmdav: convert to bytestream2 to avoid invalid reads and writes
- wavpack: check packet size early
- wavpack: use bytestream2 in wavpack_decode_block
- wavpack: validate samples size parsed in wavpack_decode_block

gst-libs/ext/libav

@@ -1 +1 @@
-Subproject commit 82c3792a308469351f0a3df20b539a9b7e6641a3
+Subproject commit 9aaca159bd220582c698f13d081a455f398c9975