Mapnik: Bugfix, really reduce list of returned columns from db query

- should have been part of commit 04cb0cc0f423a18c8189e6deeac1965d7a60ad15
Mapnik: group properties into single db column

- properties can be grouped into a single database column; therefore
  only a single string comparison is necessary. As simple tests showed,
  this is way faster (in the OpenStreetBrowser-basemap style for
  Mapnik-2.2 this reduced total rendering time by ~66%).
Eval-Functions: new functions viewport() and intersection()
Parser: Selector tests may appear in arbitrary order

closes #13
Parser: in rules, CSS does not require ; after last property

closes #12
Merge branch 'master' into josm-condition
Parser: negate class test, e.g. way!.foo
Parser/Compiler: Support pseudo classes in general; negate pseudo classes
Eval: new eval function 'is_closed'
Support pseudo class ':closed'