[libstdc++] Rename standard headers

[Phil Edwards]

Yes, Benjamin's patch is clearly correct.  In my install tree, I have
both the correct <vector> and the mistakenly installed <std_vector.h>.
Since <vector> is there, all my testing succeeded, and it shouldn't've.

Clearly something is very wrong.  I won't be making any more code/config
commits until I determine why the correct headers were mistakenly installed.

There are no plans to touch any more of this stuff before 3.2, AFAIK.
There are other headers with "odd" filenames (where "odd" == "people
complain about them"), but I myself have no plans on changing them now.


Phil