Provide const overload for VectorBasedSparseMultimap::get_all
Merge pull request #44 from TheMarex/master

Provide const overload for VectorBasedSparseMultimap::get_all
assume little endian on osx - refs #45
fix -Wunused-variable warning/errors in output
Fix -Wsign-compare warnings/errors in tests.
Add new osmium::util::double2string() function and use it.

Both Location and Coordinates classes had functions to convert doubles to
strings, doing nearly, but not quite, the same.
Use lower case for const variable, it is not a MACRO.
Use new double2string() function.
Make coordinate precision for WKT and GeoJSON configurable.

The needed precision depends on the coordinates used. For OSM coordinates in
WGS84 7 digits after the decimal point is right. For Mercator 2 digits is
enough.
fix build.bat (debug/release)
fix Boost search
remove {} initialization from osm-testdata
add osm-testdata tests
bug target