[llvm] r271491 - [LibFuzzer] Reimplement how the optional user functions are called.

[Dan Liew via llvm-commits]

> I'm going to try with an older GCC and failing that I'll try David's
> suggestion of Clang ToT.

I've managed to reproduce with GCC 4.8.

There were a few other warnings too. I've put up patches for review to
fix them all.

https://reviews.llvm.org/D35243
https://reviews.llvm.org/D35244
https://reviews.llvm.org/D35245

HTH,
Dan.