Remove legacy scripts

mapnik-osm-updater.sh was 6 years old and didn't use modern techniques,
and the SVN script isn't necessary now that osm2pgsql isn't hosted on SVN
Remove the primitive parser and fall back to libxml2

Fixes #154
Fixes #49
Remove doc references to the primitive parser
Remove buffer.cpp

Fixes #200
Remove unused pgsql_connect
Merge pull request #197 from pnorman/legacy_scripts

Remove legacy scripts
Merge pull request #204 from pnorman/pgsql_connect

Remove unused pgsql_connect
Merge pull request #203 from pnorman/buffer

Remove buffer.cpp
Merge pull request #201 from pnorman/primitive

Remove the primitive parser and fall back to libxml2