add benchmark for a single coordinate incremental lookup
disable debug code in rtree
untangle includes
Move Rectangle2DInt to own header
Add global timer utils

Global timers can be used to accumulate timings of the same context
in a thread-safe way.
Use iterators for DouglasPeucker
Allow empty ranges in DP
Make atan2_lookup inline since it is header-declared
Add wrapper function to DouglasPlucker for backwards-compability
Use numeric_limits
Fix include order in staticrtree
Reorder include and use correct datatypes