Use truffle techniques in the example

[lewurm]

This shows how to use Truffle with your Presto example. Some highlights:

• The Truffle DSL is used to add specializations.
• In order to make accesses to the Slice datastructure fast, we had to "trufflize" it a bit. For example, "Slice.getLong(int)" contains a check which, if it it fails, creates an IOOB-exception. This is quite costly and rare, thus we want to teach Truffle not to include it in a compilation (CompilerDirectives.transferToInterpreter()").
• speedup is about 2x compared to the PureJava version.

Feel free to ask if you have any questions!