Pointers vs references for out and inout parameters

[Simon Marchi]

When writing a function that modifies an object, we have two 
possibility:

declaration: void do_something (object &obj);
call: do_something (obj);

or

declaration: void do_something (object *obj);
call: do_something (&obj);

I don't think we ever ruled on which we preferred, and sometimes it's 
ambiguous during reviews which one we should use.  When reviewing one of 
Tom's patches a while ago, I suggested he uses a reference instead of a 
pointer.  His rationale for using a pointer was that it makes it more 
obvious at the call site that the object is going to be modified.

The Google C++ style guide forbids non-const reference arguments, pretty 
much for this reason [1], I think it makes sense.

I would suggest to add it to our C++ coding standards wiki page [2].

Any objection?

[1] 
https://google.github.io/styleguide/cppguide.html#Reference_Arguments
[2] 
https://sourceware.org/gdb/wiki/Internals%20GDB-C-Coding-Standards#C.2B-.2B-_Usage

Simon