Infrastructure for per-phase tests, with inline source as a string.
Merge pull request #31 from DarkDimius/tests

Infrastructure for per-phase tests, with inline source as a string.
 Enable verbose printing of exceptions thrown in junit tests
Merge pull request #32 from DarkDimius/verbose_ex

 Enable verbose printing of exceptions thrown in junit tests
For some tests context is required, it should be passed to checker phase.
More informative asserts.
Typos corrected.
More verbose assertions.
Unnecessary semicolons removed.
Add test case for #34

Right now this one fails.
Fix of #34

The root cause of #34 was that we took a type argument which was an existential type. These are returned as type bounds, which make no sense in the calling context. To avoid that problem in the future, `typeArgs`
got renamed to `argInfos`, so it is clear we get an info, not necessarily a value type. There are
also added method `argTypes`, `argTypesLo`, `argTypesHi`, which return a type, but either throw an exception or return a lower/upper approximation of the argument is an existential type.

There's another issue that the existential type only arose when compiling the same couple fo files the seciond time. We need to chase that one down separately.
Merge pull request #38 from odersky/fix/#34-pathresolvers

Fix/#34 pathresolvers
Merge pull request #35 from DarkDimius/tests-2

For some tests context is required, it should be passed to checker phase.
Merge pull request #37 from DarkDimius/assertions

Typos, better assertions, dead code
Use virtual file instead of temporary file for tests
Fix of #39

Two fixes:
1) Avoid the infinite recursion in checkAccessible if the accessibility check fails.
2) Make accessibility succeed for the test, and in general if the target denotation does not have a symbol.

Added original test in pos and a negative test which makes accessibility fail.
Merge pull request #41 from DarkDimius/virtualFile

Use virtual file instead of temporary file for tests
Got rid of SharedTree
Merge pull request #42 from odersky/fix/#39-checkAccessible

Fix of #39
Tree Transformer&TreeTransform:
1) using fast tracks in case node type isn't altered by Transformation;
2) using pre-computed hints(nxTransformXXX arrays) to quickly jump to next transformation interested in transforming particular Tree type;
3) using pre-computed hints(nxPrepareXXX arrays) to know which transformations are going to 'prepare' for transforming particular Tree type;
4) recomputing those hints in case some transformation changed implementation class during 'prepare';
5) TreeTransform is now responsible of calling transformFollowing on nodes created by it.
Merge pull request #43 from DarkDimius/tree-transformer

Tree transformer&TreeTransform
Merge pull request #45 from DarkDimius/noSharedTrees

Get rid of SharedTree