fix compilation with --disable-everything --enable-decoder=twinvq

Originally committed as revision 22479 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/Makefile

@@ -333,7 +333,7 @@ OBJS-$(CONFIG_TRUEMOTION2_DECODER)     += truemotion2.o
 OBJS-$(CONFIG_TRUESPEECH_DECODER)      += truespeech.o
 OBJS-$(CONFIG_TSCC_DECODER)            += tscc.o msrledec.o
 OBJS-$(CONFIG_TTA_DECODER)             += tta.o
-OBJS-$(CONFIG_TWINVQ_DECODER)          += twinvq.o
+OBJS-$(CONFIG_TWINVQ_DECODER)          += twinvq.o celp_math.o
 OBJS-$(CONFIG_TXD_DECODER)             += txd.o s3tc.o
 OBJS-$(CONFIG_ULTI_DECODER)            += ulti.o
 OBJS-$(CONFIG_V210_DECODER)            += v210dec.o