r.mapcalc manual: fix if() statement formula (trac https://trac.osgeo.org/grass/ticket/2883)

git-svn-id: https://svn.osgeo.org/grass/grass/branches/releasebranch_7_0@67787 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.mapcalc/r.mapcalc.html

@@ -646,9 +646,9 @@ To mask raster map layer <em>b</em> by raster map layer <em>a</em>:
 <div class="code"><pre>
 result = if(a,b)
 </pre></div>
-To change all values below 5 to NULL:
+To change all values below 5 to NULL, keep otherwise:
 <div class="code"><pre>
-newmap = if(map&lt;5, null(), 5)
+newmap = if(map &lt; 5, null(), map)
 </pre></div>
 The graph() function allows users to specify a x-y conversion using 
 pairs of x,y coordinates.

raster/r.mapcalc/r3.mapcalc.html

@@ -166,6 +166,7 @@ result = x@PERMANENT / y@SOILS
 GRASS commands, not just <em>r3.mapcalc</em>.)
 <p>
 
+
 <h3>The neighborhood modifier</h3>
 
 3D grids are data base files stored in voxel format, i.e., three-dimensional
@@ -517,9 +518,9 @@ To mask 3D grid <em>b</em> by 3D grid <em>a</em>:
 <div class="code"><pre>
 result = if(a,b)
 </pre></div>
-To change all values below 5 to NULL:
+To change all values below 5 to NULL, keep otherwise:
 <div class="code"><pre>
-newmap = if(map&lt;5, null(), 5)
+newmap = if(map &lt; 5, null(), map)
 </pre></div>
 The graph() function allows users to specify a x-y conversion using 
 pairs of x,y coordinates.