noise from gcc.dg/torture/fp-convert tests

[Eric Christopher]

> Eric, Do you mean that they're noisy because of the WARNINGs?  I always
> find warnings annoying, perhaps test_summary should filter them out.

Yeah, that's what I meant.

> Notice that for -m32, the message from the linker includes "In function
> `main':"; this causes prune_gcc_output to remove that line of output,
> which results in the failure not being recognized.  I wonder how many
> targets this affects, and how many link failures are not recognized
> because of it.

Ick.

-eric