keep databases open, close db cursors, initial block download in batches of 500 blocks, fix misc warnings, subver linux-test8 git-svn-id: https://bitcoin.svn.sourceforge.net/svnroot/bitcoin/trunk@40 1a98c847-1fd6-4fd8-948a-caf3550aa51b
git-svn-id: https://bitcoin.svn.sourceforge.net/svnroot/bitcoin/trunk@36 1a98c847-1fd6-4fd8-948a-caf3550aa51b
git-svn-id: https://bitcoin.svn.sourceforge.net/svnroot/bitcoin/trunk@32 1a98c847-1fd6-4fd8-948a-caf3550aa51b