Automatic dependency tracking

[Joel Brobecker]

> Option two: we could require GNU make.  GCC has done this for years,
> but binutils does not; it may be premature.

I think it's reasonable to require GNU make to build GDB. On all
the platforms that we have here at AdaCore, we've never had any
problem getting our hands on a recent version of GNU make. Hopefully,
that's representative of the availability of that tool.

-- 
Joel