env.bat: fix R temporarily set to %PATH% in windows

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@66766 15284696-431f-4ddb-bdfa-cd5b030d7da7

mswindows/env.bat

@@ -18,3 +18,8 @@ set GEOTIFF_CSV=%GISBASE%\share\epsg_csv
 set PATH=%GISBASE%\msys\bin;%PATH%
 set PATH=%GISBASE%\extrabin;%PATH%
 set PATH=%GISBASE%\bin;%PATH%
+
+REM set R temporarily to %PATH%
+
+cd %GISBASE%\extrabin
+R path