RFC libstdc++-v3 -> libstdc++ rename

[Benjamin Kosnik]

Yo dudes. I'm thinking now or soon from now is the time for this. 

For the last five years, libstdc++-v3 has been the default C++ library
for GCC. When this transition first went down, "libstdc++-v3" was used
as the top level designation because of some cvs-specific issues that
Ang and I had (well, mostly her since I'd messed up the first merge
attempt) trying to merge libstdc++-v3 as libstdc++. In addition, it was
a nice, non-ambiguous way to separate the new and old code.

There is no longer a need for this designation, and subversion
supposedly handles renames well.

So, it seems in the realm of the possible. 

Thoughts? I realize this is low on the priority list. But, I'm curious
to see what the reaction is, and if there is a firm consensus for or
against.

-benjamin