Debugger: Remove needless explicit copy constructors.

These worked in identical fashion to what the default copy
constructors would be, but their mere presence marks the class
as being "non-trivially copyable," which means that memcpy'ing
it is now a -Werror on GCC 8.

We have to be careful when making this change, though: classes
which *are* trivially copyable can be passed inside registers
on x86_64, so changes like these break ABI in a dangerous way.
These classes is private, so it should not be a problem, but
for other classes (e.g. BRect, BPoint) we cannot fix them
properly right now.

headers/private/debugger/arch/Register.h

@@ -32,7 +32,6 @@ public:
 									uint32 bitSize, uint32 valueType,
 									register_type type, bool calleePreserved);
 										// name will not be cloned
-								Register(const Register& other);
 
 			int32				Index() const		{ return fIndex; }
 			const char*			Name() const		{ return fName; }