improve split algo:
The test generator is > 10 times faster. This allows a deeper 
search for good splits. A few errors where fixed which
sometimes prohibited to find a good split, but also sometimes
helped to find one. 

A new option --search-limit can be used to increase/decrease the
amount of time the splitter tries to find a good split.
The larger the input file the higher this value should be.
For planet, --search-limit=1000000 is okay, --search-limit=10000000
is better.

git-svn-id: http://svn.mkgmap.org.uk/splitter/trunk@390 838fabe5-b1a8-4b81-9896-7a84386980e9
remove unintended import

git-svn-id: http://svn.mkgmap.org.uk/splitter/trunk@391 838fabe5-b1a8-4b81-9896-7a84386980e9
improve handling of --polygon-file or --polygon-desc-file :


git-svn-id: http://svn.mkgmap.org.uk/splitter/trunk@392 838fabe5-b1a8-4b81-9896-7a84386980e9