add a separate line in Makefile for E-AC-3 decoder and only compile it when

GPL is enabled. fixes building without GPL or with liba52.

Originally committed as revision 15151 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -848,6 +848,7 @@ byteswap_h_deps="!armv4l"
 # decoders / encoders
 ac3_decoder_deps="gpl !liba52"
 dxa_decoder_deps="zlib"
+eac3_decoder_deps="gpl"
 flashsv_decoder_deps="zlib"
 flashsv_encoder_deps="zlib"
 mlp_decoder_deps="mlp_parser"

libavcodec/Makefile

@@ -63,6 +63,7 @@ OBJS-$(CONFIG_DVDSUB_ENCODER)          += dvdsubenc.o
 OBJS-$(CONFIG_DVVIDEO_DECODER)         += dv.o
 OBJS-$(CONFIG_DVVIDEO_ENCODER)         += dv.o
 OBJS-$(CONFIG_DXA_DECODER)             += dxa.o
+OBJS-$(CONFIG_EAC3_DECODER)            += eac3dec.o ac3dec.o ac3tab.o ac3dec_data.o ac3.o mdct.o fft.o
 OBJS-$(CONFIG_EACMV_DECODER)           += eacmv.o
 OBJS-$(CONFIG_EATGV_DECODER)           += eatgv.o
 OBJS-$(CONFIG_EIGHTBPS_DECODER)        += 8bps.o