r.watershed manual: (minor) sync with trunk

git-svn-id: https://svn.osgeo.org/grass/grass/branches/releasebranch_7_0@60855 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.watershed/front/r.watershed.html

@@ -55,7 +55,8 @@ analysis is based. NULL (nodata) cells are ignored, zero and negative
 values are valid elevation data.  Gaps in the elevation map that are
 located within the area of interest must be filled beforehand,
 e.g. with <em><a href="r.fillnulls.html">r.fillnulls</a></em>, to
-avoid distortions.
+avoid distortions.  The elevation map need not be sink-filled because
+the module uses a least-cost algorithm.
 
 <p>
 Map of actual depressions or sinkholes in the landscape that are large
@@ -113,7 +114,7 @@ their surface runoff and sedimentation yields calculated accurately.
 <p>
 Output <b>tci</b> raster map contains topographic index TCI is
 computed as
-<tt>ln(&alpha; / tan(&beta;))</tt> where &alpha; a is the cumulative
+<tt>ln(&alpha; / tan(&beta;))</tt> where &alpha; is the cumulative
 upslope area draining through a point per unit contour length and
 <tt>tan(&beta;)</tt> is the local slope angle. The TCI reflects the
 tendency of water to accumulate at any point in the catchment and the