Make dumpers pass on more size information initially, namely the
various Q<>Pointers. Introduce enum for those special template types
whose size does not vary with the arguments (Q<>Pointer,
std::allocators...) to make it more easily extensible.
Pass on some common QMapNode<> sizes as well.
Introduce an expression cache to the common QtDumperHelper
class and make dumpers pass some common expression values
(value offsets of common QMapNode<> incarnations).
Make CDBDumperHelper use the expression cache.
Extend dumper tester.
Do not trigger the whole debugger mechanism when Dumpers
crash on encountering uninitizialized variables. Temporarily
ignore the exceptions while in dumper call.
