Fix #167

Can handle now vararg arguments in patterns.
Merge pull request #168 from dotty-staging/fix/#167

Fix #167
Changes from discussion in #171
Allow converting junit test to scalameter benchmark

Lets start tracking performance!

To run benchmarks execute `dotty-bench/test:run` in sbt
Definitions used by pattern matcher
initValue helper method
Making all case classes implement Product. Requires adding Product0
Unapply doc update
More complicated patterns.
Definitions used by patmat
Common functionality to be shared between patmat and typer
CommonCodegen for patMat
Optimized codegen for patmat
TreeMakers for patmat
add Substitution to patmat.
Some compilation errors fixed
Match translator for patmat
Pattern expanders for patmat
Helper methods for patmat
Adapting patmat for dotty
more of adapting patmat for dotty