Preserve the CWD when showing the file open/save dialog.

git-svn-id: http://tortoisesvn.googlecode.com/svn/trunk/src/TortoiseMerge@23925 4cfb86a4-2c7a-11df-bd14-c1e331e6ceac
Update the line diff bar when scrolling.

git-svn-id: http://tortoisesvn.googlecode.com/svn/trunk/src/TortoiseMerge@23939 4cfb86a4-2c7a-11df-bd14-c1e331e6ceac