Add LSL transaction_result event.

This is cinderblocks' transaction_result.diff from http://opensimulator.org/mantis/view.php?id=7329 but I have used lsl.parser.cs and lsl.lexer.cs files generated directly from opensim-libs rather than those supplied in the patch.
I also added scriptEvents.transaction_reuslt.
The required parser/lexer generation file changes were made in commit d564f28 in the opensim-libs repo.
Thanks!