Install all backward headers?

[Benjamin Kosnik]

> Due to Benjamin's recent work in the area, I just noticed that way
> back in May when I added some new backward headers to allow more
> "traditional" g++ test cases to pass that I forgot to update
> src/Makefile.am to install them.

I just did this. Thanks for pointing it out. I'd not noticed it yesterday.

> Do we want: complex.h, iomanip.h, istream.h, ostream.h, stream.h and
> streambuf.h to be installed in backward?  Or, are they just supposed
> to be useful to pass old g++ test cases?

All the 'backward' headers are now grouped in one place in the source 
tree, ie include/backward. I think this makes more sense.

They are now all installed in include/backward as well.

-benjamin