Removed some dead broken code

The compiler does not have a getVariableCompiler method anymore. The
VariableExpression is handled by a type compiler.
Removed the unused itemType property in the compiler

There is no way to write in this private property so the isset check would
always return false.
Thus, this feature was flawed as it would not handle inheritance (checking
for parent classes or interfaces for instance).
Merge pull request #109 from stof/dead_code

Removing some dead code