Add rvalue references to overloading resolution

Add rvalue references to overloading resolution

This patch introduces changes to rank_one_type() dealing with ranking an rvalue
reference type when selecting a best viable function from a set of candidate
functions. The 4 new added rules for rvalue references are:

1) An rvalue argument cannot be bound to a non-const lvalue reference parameter
and an lvalue argument cannot be bound to an rvalue reference parameter.
[C++11 13.3.3.1.4p3]

2) If a conversion to one type of reference is an identity conversion, and a
conversion to the second type of reference is a non-identity conversion, choose
the first type. [C++11 13.3.3.2p3]

3) An rvalue should be first tried to bind to an rvalue reference, and then to
an lvalue reference. [C++11 13.3.3.2p3]

4) An lvalue reference to a function gets higher priority than an rvalue
reference to a function. [C++11 13.3.3.2p3]

This patch is not exactly correct.  See c++/15372 for tracking overload
resolution bugs.

gdb/ChangeLog

	PR gdb/14441
	* gdbtypes.c (rank_one_type): Implement overloading
	resolution rules regarding rvalue references.