How to not fold constants?

[Joern Rennecke]

> I think an easier (and more obvious IMHO) solution is to have the C
> frontend "Do The Right Thing", i.e. call build(fold(...)) in case of a
> static initializer and build(...) otherwise [or is there a snag in there
> that I'm overlooking ?]

Yes.  There might be integer expressions inside that we want to fold.
We also want to fold floating point if this can be done without an
inexact operation or generating NaNs.