Travis: Use Launchpad PPA for LLVM 3.3; the llvm.org repo no longer has it.

.travis.yml

@@ -1,8 +1,16 @@
 language: cpp
 install:
+  # LLVM 3.2
   - sudo sudo sh -c "echo 'deb http://archive.ubuntu.com/ubuntu/ precise-proposed restricted main multiverse universe' >> /etc/apt/sources.list"
+
+  # LLVM 3.4 snapshots
   - sudo sudo sh -c "echo 'deb http://llvm.org/apt/precise/ llvm-toolchain-precise main' >> /etc/apt/sources.list"
   - wget -O - http://llvm.org/apt/llvm-snapshot.gpg.key | sudo apt-key add -
+
+  # Some random Launchpad PPA for LLVM 3.3, should consder replacing this with
+  # the official Clang binary package from the llvm.org download page.
+  - echo yes | sudo add-apt-repository ppa:nmi/llvm-3.3
+
   - sudo apt-get update -qq
   - sudo apt-get install -qq $LLVM_PACKAGE libconfig++8-dev
   - if [[ "${OPTS}" == *MULTILIB*ON* ]]; then sudo apt-get install -qq gcc-multilib libcurl3:i386 ; fi