"all rights reserved" and GPL

[Shriramana Sharma <samjnaa@gmail.com>]

Hello. In the license header of a source file being licensed under the 
GPL, there must be a copyright notice. Sometimes I see the usage of "All 
rights reserved" in that notice:

// Copyright (C) 2007, Company X. All rights reserved.

1) Is the usage of "All rights reserved" appropriate when a file is 
being licensed under the GPL, or in fact under whatever license?

2) What is the purpose of its usage?

3) If it is that the licensor wants to say: "Any rights I have not 
explicitly given you, you do not have"?

4) If so, would it not be necessary, strictly speaking, to say so, i.e. 
"All rights regarding this work, unless explicitly granted to the 
licensee, are reserved by the licensor"? "All rights reserved" seems to 
be inappropriate, if not incorrect, when in fact all rights are *not* 
reserved.

5) Is it *advisable* to use such a terminology in a copyright statement 
in a file licensed under the GPL?

Thanks for your thoughts.

Shriramana Sharma.