VB code completion: fix bug that caused code completion to omit local variables when typing near the end of a block.

http://community.sharpdevelop.net/forums/t/16643.aspx
The VB parser was using the end of the last statement as the EndLocation for the block. This made local variables
declared in that block unavailable when typing another statement at the end of the block.
We now use the location of the 'End' or 'Next' token instead.