[libstdc++] Update comments in testsuite files, add dummy tool file.

[Gabriel Dos Reis]

Phil Edwards <phil@jaj.com> writes:

| 	* testsuite/lib/libstdc++-v3.exp:  New file.

Err, Phil, what you wanted is testsuite/lib/libstdc++-v3-dg.exp.  It
just got the wrong file name.  The right fix is to rename that file,
not put a nearby empty file.  Please, rename libstdc++-v3-dg.exp to
libstdc++-v3.exp. 

-- Gaby