Decoupling -O from -fvia-C

[Wolfgang Thaller]

> may be it's better to start with speed tests?

What would that achieve, given that the decision does not depend on  
speed measurements? The argument "implicit -fvia-C makes things  
refuse to work" is stronger than the argument "-fvia-C makes things x 
% faster on platform Y, so it should be on by default", for all  
values of x and y.

That said, speed tests are always a good thing, as long as I don't  
have to do them myself ;-).

Cheers,

Wolfgang