Fixed bugs for LLVM/Clang 3.3.

* .gitignore: Fixed bugs because the filename of the Clang source tarball
  has been changed from `clang-x.y.src.tar.gz` to `cfe-x.y.src.tar.gz` since
  LLVM/Clang 3.3.
* clang/jamfile:
  * Likewise.
  * Extra Clang Tools has been bundled with LLVM/Clang releases since 3.3.
    However, they seem unstable especially with debug builds. Therefore,
    the build scripts for them has been added but still commented out.