lavc/tiff: Decode embedded JPEGs in DNG images

Used a technique similar to lavc/tdsc.c for invoking the MJPEG decoder.

This commit adds support for:
- DNG tiles
- DNG tile huffman lossless JPEG decoding
- DNG 8-bpp ("packed" as dcraw calls it) decoding
- DNG color scaling [1]
  - LinearizationTable tag
  - BlackLevel tag

[1]: As specified in the DNG Specification - Chapter 5
Signed-off-by: Nick Renieris <velocityra@gmail.com>

configure

@@ -2821,6 +2821,7 @@ tdsc_decoder_deps="zlib"
 tdsc_decoder_select="mjpeg_decoder"
 theora_decoder_select="vp3_decoder"
 thp_decoder_select="mjpeg_decoder"
+tiff_decoder_select="mjpeg_decoder"
 tiff_decoder_suggest="zlib lzma"
 tiff_encoder_suggest="zlib"
 truehd_decoder_select="mlp_parser"

libavcodec/Makefile

@@ -618,7 +618,7 @@ OBJS-$(CONFIG_TARGA_ENCODER)           += targaenc.o rle.o
 OBJS-$(CONFIG_TARGA_Y216_DECODER)      += targa_y216dec.o
 OBJS-$(CONFIG_TDSC_DECODER)            += tdsc.o
 OBJS-$(CONFIG_TIERTEXSEQVIDEO_DECODER) += tiertexseqv.o
-OBJS-$(CONFIG_TIFF_DECODER)            += tiff.o lzw.o faxcompr.o tiff_data.o tiff_common.o
+OBJS-$(CONFIG_TIFF_DECODER)            += tiff.o lzw.o faxcompr.o tiff_data.o tiff_common.o mjpegdec.o
 OBJS-$(CONFIG_TIFF_ENCODER)            += tiffenc.o rle.o lzwenc.o tiff_data.o
 OBJS-$(CONFIG_TMV_DECODER)             += tmv.o cga_data.o
 OBJS-$(CONFIG_TRUEHD_DECODER)          += mlpdec.o mlpdsp.o

libavcodec/tiff.h

@@ -101,6 +101,8 @@ enum TiffTags {
 enum DngTags {
     DNG_VERSION             = 0xC612,
     DNG_BACKWARD_VERSION    = 0xC613,
+    DNG_LINEARIZATION_TABLE = 0xC618,
+    DNG_BLACK_LEVEL         = 0xC61A,
     DNG_WHITE_LEVEL         = 0xC61D,
 };