Fix warnings in test code:

eval.c:454: warning: return type defaults to 'int'
eval.c:464: warning: control reaches end of non-void function

Originally committed as revision 11594 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/eval.c

@@ -451,7 +451,7 @@ static const char *const_names[]={
     "E",
     0
 };
-main(void){
+int main(void){
     int i;
     printf("%f == 12.7\n", ff_eval("1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)", const_values, const_names, NULL, NULL, NULL, NULL, NULL));
     printf("%f == 0.931322575\n", ff_eval("80G/80Gi", const_values, const_names, NULL, NULL, NULL, NULL, NULL));
@@ -461,5 +461,6 @@ main(void){
             ff_eval("1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)", const_values, const_names, NULL, NULL, NULL, NULL, NULL);
         STOP_TIMER("ff_eval")
     }
+    return 0;
 }
 #endif