[grass/f15] (6 commits) ...Merge branch 'master' into f15

[Volker Fröhlich]

Summary of changes:

  c0b3154... UPDATE FOR 6.4.1 (*)
  1137336... ADD SOURCE (*)
  357b526... NEW VERSION, GENERAL CLEAN-UP, WORKING LOCALES AND DOCS (*)
  2cf3b76... MOVE SED CALLS BACK TO INSTALL SECTION (*)
  fbffd08... ADD LIBPNG API PATCH (*)
  eeea4bd... Merge branch 'master' into f15

(*) This commit already existed in another branch; no separate mail sent