Allow to get a TClass instance via typedef name w/o parsing

performing the following steps:
0) Autoload based using the name of the typedef as key (was there already)
1) Check if the name is a typedef
2) If yes, try to get in the class table the TClass linked to the underlying
type. Do not use a nested GetClass call.
Avoid parsing if possible even if the user allows for it
Remove shadowing of parameter