Fix av_compare_mod() doxy.

Originally committed as revision 23593 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/mathematics.h

@@ -95,12 +95,14 @@ int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq) av_const;
 int av_compare_ts(int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b);
 
 /**
- * Compare 2 integers modulo mod.
- * That is we compare integers a and b for which only the least significant log2(mod) bits are known
+ * Compares 2 integers modulo mod.
+ * That is we compare integers a and b for which only the least
+ * significant log2(mod) bits are known.
+ *
  * @param mod must be a power of 2
- * @returns a negative value if a is smaller than b
- *          a positiv  value if a is greater than b
- *          0                if a equals          b
+ * @return a negative value if a is smaller than b
+ *         a positive value if a is greater than b
+ *         0                if a equals          b
  */
 int64_t av_compare_mod(uint64_t a, uint64_t b, uint64_t mod);