Move to new LLVM version

[PeterMatula]

Version of LLVM we use is pretty old (3.9.1). We should move to the new LLVM sooner rather than later.

[MerovingianByte]

Wouldn't it be possible to talk to the LLVM guys to provide more options to disable optimizations and stuff so that retdec can use vanilla LLVM instead of hacking it? Maybe it would save time in the long run. I mean, I'm just curious, not my business.

[s3rvac]

@MerovingianByte Frankly speaking, I do not see this as realistic. We have many changes throughout the entire codebase, and their conditional inclusion would seriously clutter the code. Never say never, though :-).

[s3rvac]

LLVM 6.0 is out.

[s3rvac]

LLVM 7.0 is out.

[s3rvac]

LLVM 8.0 is out.

[sskras]

Are other changes not linked to this commit?

[PeterMatula]

This was fixed by merging llvm-8 branch in llvm repo: avast/llvm@82632c5
and in retdec repo: 7a2018b