Changes in build organization

 * targets are now created in top-level build directory
 * more things are now configured through CMake options
 * changed debug build detection from NDEBUG to DEV_BUILD
 * moved po and desktop directories
 * moved last unit test out of src directory
Fix man build target dependencies

 * could cause fails when make is run with many threads
Futher changes to CMake options

 * OpenAL sound is now enabled by default
 * Boost is linked dynamically by default
gitignore update

 * git should now ignore all generated files when building without
   separate build directory
Updated INSTALL files
Fix for MSYS/MXE build
Fixed auto-detecting locale on Windows

 * localename library is now used to determine the actual locale used
 * added patched version of FindGettext.cmake to fix
   installation path of translation files
Some further changes in CMakeLists

 * removed DEV_BUILD autodetection (could be confusing)
 * ignore desktop subdirectory on Windows
 * some refactoring