build: Add config option for CABAC code

This allows for more elegant dependency and object declarations.

configure

@@ -1512,6 +1512,7 @@ CONFIG_EXTRA="
     aandcttables
     ac3dsp
     audio_frame_queue
+    cabac
     dsputil
     gcrypt
     golomb
@@ -1748,9 +1749,9 @@ h263_decoder_select="error_resilience h263_parser h263dsp mpegvideo"
 h263_encoder_select="aandcttables h263dsp mpegvideoenc"
 h263i_decoder_select="h263_decoder"
 h263p_encoder_select="h263_encoder"
-h264_decoder_select="golomb h264chroma h264dsp h264pred h264qpel videodsp"
+h264_decoder_select="cabac golomb h264chroma h264dsp h264pred h264qpel videodsp"
 h264_decoder_suggest="error_resilience"
-hevc_decoder_select="dsputil golomb videodsp"
+hevc_decoder_select="cabac dsputil golomb videodsp"
 huffyuv_decoder_select="dsputil"
 huffyuv_encoder_select="dsputil huffman"
 iac_decoder_select="imc_decoder"

libavcodec/Makefile

@@ -29,6 +29,7 @@ OBJS = allcodecs.o                                                      \
 OBJS-$(CONFIG_AANDCTTABLES)            += aandcttab.o
 OBJS-$(CONFIG_AC3DSP)                  += ac3dsp.o
 OBJS-$(CONFIG_AUDIO_FRAME_QUEUE)       += audio_frame_queue.o
+OBJS-$(CONFIG_CABAC)                   += cabac.o
 OBJS-$(CONFIG_DCT)                     += dct.o dct32_fixed.o dct32_float.o
 OBJS-$(CONFIG_DXVA2)                   += dxva2.o
 OBJS-$(CONFIG_DSPUTIL)                 += dsputil.o faanidct.o          \
@@ -197,11 +198,10 @@ OBJS-$(CONFIG_H263_ENCODER)            += mpeg4videoenc.o mpeg4video.o  \
 OBJS-$(CONFIG_H264_DECODER)            += h264.o h264_cabac.o h264_cavlc.o \
                                           h264_direct.o h264_loopfilter.o  \
                                           h264_mb.o h264_picture.o h264_ps.o \
-                                          h264_refs.o h264_sei.o h264_slice.o \
-                                          cabac.o
+                                          h264_refs.o h264_sei.o h264_slice.o
 OBJS-$(CONFIG_HEVC_DECODER)            += hevc.o hevc_mvs.o hevc_ps.o hevc_sei.o \
                                           hevc_cabac.o hevc_refs.o hevcpred.o    \
-                                          hevcdsp.o hevc_filter.o cabac.o
+                                          hevcdsp.o hevc_filter.o
 OBJS-$(CONFIG_HNM4_VIDEO_DECODER)      += hnm4video.o
 OBJS-$(CONFIG_HUFFYUV_DECODER)         += huffyuv.o huffyuvdec.o
 OBJS-$(CONFIG_HUFFYUV_ENCODER)         += huffyuv.o huffyuvenc.o