[OSM-dev] osm2pgsql build system switched to cmake

[Paul Norman]

The osm2pgsql build system has been switched from autotools to cmake. 
This means that anyone automatically building the latest version will 
need to switch their scripts.

In particular, they will need to
- Clean out old files (git clean -xfd will do this, but also remove 
*any* untracked files)
- build with mkdir build && cd build && cmake .. instead of ./autogen.sh 
&& ./configure
- convert any configure options into cmake options

The README has more info, and CMake is a commonly used build tool so 
there is plenty of information on it online.

If there are any new issues, please check for tickets at 
https://github.com/openstreetmap/osm2pgsql/issues and if needed, open a 
new one.

A couple of changes are

- CMake enables optimization by default, which should make osm2pgsql 
faster when it is CPU bound
- Windows builds should be much easier, and I hope to be producing them 
regularly