Document the same functions, in the same order, that eval.c has.

Originally committed as revision 16586 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/ffmpeg-doc.texi

@@ -838,16 +838,22 @@ The following functions are available:
 @item sin(x)
 @item cos(x)
 @item tan(x)
+@item atan(x)
+@item asin(x)
+@item acos(x)
 @item exp(x)
 @item log(x)
+@item abs(x)
 @item squish(x)
 @item gauss(x)
-@item abs(x)
+@item mod(x, y)
 @item max(x, y)
 @item min(x, y)
+@item eq(x, y)
+@item gte(x, y)
 @item gt(x, y)
+@item lte(x, y)
 @item lt(x, y)
-@item eq(x, y)
 @item bits2qp(bits)
 @item qp2bits(qp)
 @end table