as.info built in the source directory?

[Ben Elliston]

This has been bugging me for a while.  I'm not sure what the correct
behaviour is.  My instinct is that the derived object, as.info, should
be built in the build directory and installed from there, but then I
don't know how this interacts with make dist, which should be
including as.info in the distribution.

Can anyone clarify?  I'm happy to try and fix it, as I prefer to keep
my source trees pristine!

Ben