LLVM 3.0 support

[David Nadlinger]

Hi all,

How long do we want to keep support for LLVM 3.0?

I'd love to drop it right now, as LLVM 3.0 defined a "-float-abi" 
command line switch in TargetMachine.cpp, conflicting with our 
new one. It also entails quite some maintenance effort to write 
around the missing pieces of the API. And this is not considering 
the fact that the optimizer, etc. improvements in LLVM 3.1–3.3 
actually lead to quite an improvement for LDC users as well.

IMHO, the only reason to keep it would be to support building 
against the outdated LLVM distro packages e.g. in Debian, but 
since LLVM is easy to build locally while packaging (LDC), I am 
not sure how much of an argument this is anyway.

Also, several interesting new developments in LDC (Windows/MinGW, 
ARM, …) will require LLVM 3.3+ anyway.

David