Issue #1325: Add a new kind of test based around tracing the execution of a ceylon program,
and making assertions about the methods and lines that are stepped through.

This is a little tricky because we don't want to add tools.jar to
the classpath, since that breaks the compiler tests (and the compiler). We
leap though this hoop by keeping TracerImpl.java off the source path
and compiling it in DebuggerTest.
Issue #1325: Add AssertFalse.ceylon
Issue #1325: Fix position of assert(false) and assert(anythingelse)
ws
Issue #1325: Fix the position of various synthetic things.
Forgot test for #1334
AbstractTransformer: consider qualifying types when looking at rawness (#1330)
Test for: Fatal error for self type + Iterable.filter (#1330)
CodegenUtil: consider actual classes the same as aliases wrt resovling refined parameters (#1332)
gitignore: added more trace class files
Test for: Seltype constructor with different parameter name => Fatal Error (#1332)
Fix #1324
Issue #1324: Fix tests.
ExpressionTransformer.erasure/boxing: make sure downcasts get at least one cast (#1336)

In some cases it could have happened that we didn't even add one
Test for: CompilerBugException: assert nonempty with union types sequencial (#1336)
AbstractTrasnformer.makeTypeParameter: substitute refined type parameter bounds (#1328)
Test for: "Cannot find" superinterface type parameter (#1328)
Now using constants for System property and environment variable names