grass-64: keg-only; only tcltk for gui; update syntax
grass-64: keg-only; only tcltk for gui; update syntax

- wxwidgets 2.8 can not be reliably installed on 10.6-9, so fall back to only tcl-tk gui

OSGeo/homebrew-osgeo4mac,OSGeo/homebrew-osgeo4mac,OSGeo/homebrew-osgeo4mac