Add emms_c() after exp_diff calculations.

Fixes AC-3 encoding on OpenBSD 4.8 x86_32 and hopefully other similar
configurations.

Originally committed as revision 26070 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/ac3enc.c

@@ -587,6 +587,7 @@ static void compute_exp_strategy_ch(AC3EncodeContext *s, uint8_t *exp_strategy,
         else
             exp_strategy[blk] = EXP_REUSE;
     }
+    emms_c();
 
     /* now select the encoding strategy type : if exponents are often
        recoded, we use a coarse encoding */