Debugger: Have 64bit debuggers handle 32bit targets, too

Prefer 32bit debuggers if possible though. In the setup Robert
used there is only a 64bit CDB and thus the debugger of his
64bit Qt was unset.

Add unit tests to make sure changes will not effect currently
working setups.

Task-number: QTCREATORBUG-10463
Change-Id: I4afae314bc75d4465dbc8de5b2a4267a521a4ea1
Reviewed-by: hjk <hjk121@nokiamail.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Debugger: Work around strange GDB behavior with overload resolution

Contrary to the documention, using the default (i.e. 'on') it seems to _require_
xplicit casting of function pointers:
 (gdb) p &Myns::QMetaType::typeName
    -> $1 = (const char *(*)(int)) 0xb7cf73b0 <Myns::QMetaType::typeName(int)>
 (gdb) p Myns::QMetaType::typeName(1024)
     -> 31^error,msg="Couldn't find method Myns::QMetaType::typeName"
But we can work around on the dumper side. So let's use the default from now on.

Change-Id: I3e2a87df797c6abab6183b4c121b843e5035cd47
Reviewed-by: hjk <hjk121@nokiamail.com>
Debugger: Leave GDB default setting for 'set overload resolution'

... and work around the pecularities on the dumper side instead.

Change-Id: I0c2703aae13dabc0f3f45efb46bd556c8741a15f
Reviewed-by: hjk <hjk121@nokiamail.com>
Debugger: Some autotest cosmetics

Change-Id: Ib174e84f97511b28cd7649c219a62fe606186bf2
Reviewed-by: hjk <hjk121@nokiamail.com>