Removed use of boost::test_tools::output_test_stream.

This was a relict from when we used boost unit tests.
Mention that libosmium now works in Windows in README.
Explicitly handle all types when iterating over children of Area.
Only disable warnings for OGR header that the compiler knows about.
Add tests for coordinate2string function.
Suppress warnings from OGR code.
Ignore float-equal warning in catch.hpp.
Fix more integer casts.
Suppress warnings from OGR code in examples.
Put ignore pragma in a place that it doesn't effect code outside catch.hpp.
Libosmium doesn't work with GCC 4.7 any more.
Fix integer type warnings in test.
Refactoring warning flags.

Add more warning flags and turn them into errors. Use only some warnings on g++
vs. clang++.