[Patch, libgfortran] Better format hash function

[Paolo Bonzini]

Janne Blomqvist wrote:
> Hi,
> 
> the attached patch replaces the existing (too?) simple string hash
> function with an almost equally simple but supposedly pretty well
> working one by D.J. Bernstein.

It's quite overrated (first collision took 30 seconds to find by hand: 
C# collides with BD), but it cannot be worse than what is there now.

Paolo