Update to LLVM 3.4 for the 0.3 release

[ViralBShah]

I have been using LLVM 3.4 for a while, and it seems to work just fine. There are only a few issues that may need addressing (#6635, #6757, #6369) to make LLVM 3.4 default.

If 0.3 is still a few weeks away, it may be worthwhile to update to 3.4. We could then potentially have Julia 0.3 on ARM (#3134).

[Keno]

I object somewhat strongly. We've been running on 3.3 reliably for a while and this is not the time to experiment. We can do that the first thing after 0.3 is released.

[tkelman]

Anything other than 3.3 is nonfunctional on Windows right now.

Here's 3.4 from a few weeks ago: https://gist.github.com/tkelman/11294079
And here's 3.5 svn from a few days ago: https://gist.github.com/tkelman/1d0edd8809aecc975cb9

[ViralBShah]

@tkelman I had missed the Windows issue. Thanks.

[cmundi]

Even if the windows issues did not exist, I would object to ignoring the regressions on Linux and MacOS. In particular #6369 may seem obscure, but a deep regression which impacts Cairo (and therefore Gadfly) could delay Julia adoption by folks who cannot or prefer not to visualize their data in their heads. ;) Until the Julia regression suite coverage is much greater than it is today, these canaries in the coal mine should be treated as serious until proved innocuous.