Add llvm-config-3.4 to list of llvm-config names.

The LLVM 3.4 development ccycle has started. We should be prepared
for a distribution which starts to use this name.
Add LLVM 3.2/3/4 to Travis CI.

Changes the Travis CI configuration to use the following packages:
- LLVM 3.1 from precise
- LLVM 3.2 from precise-proposed
- LLVM 3.3 and 3.4 from llvm.org snapshot

LLVM 3.4 builds are allowed to fail because this is a development snaphot.
Reorganizes the cmake command line, too.
Merge pull request #399 from redstar/travis

Add LLVM 3.2/3/4 to Travis CI.
Make ldmd compatible with LLVM 3.4

Development of LLVM 3.4 started with a cleanup of the path class (PathV1).
The changes here let ldmd compile at least with rev. 184039 of LLVM.
Merge pull request #400 from redstar/ldmd34

Make ldmd compatible with LLVM 3.4
Make ldc compatible with LLVM 3.4

Development of LLVM 3.4 started with a cleanup of the path class (PathV1).
The changes here let ldc compile at least with rev. 184039 of LLVM.