The BIG graph update

  * Replace libgd with libart
  * Added freetype
  * Updated zlib and libpng
  * rrd_gfx.c intrduced as libart wrapper
  * LINE takes now a float as argument
  * rrdtool uses truetype for fonts
  * thanks to libart there is now full alpha transparenc
    and antialiasing.
  * the new option --font lets customize the font
    and size for various graph elements
  * Updated to -> libtool 1.4.2 automake 2.12 autoconf 2.52
  * new --zoom commandline option for zoom ans shrinking
  -- tobias oetiker

git-svn-id: svn://svn.oetiker.ch/rrdtool/trunk/program@61 a5681a0c-68f1-0310-ab6d-d61299d08faa