CMake: Fixed the LLVM version regex

When trying to KLEE with a version of LLVM (specifically, 3.5) built from
Github (https://github.com/llvm-mirror/llvm/tree/release_35) the regex in
find_llvm.cmake failed to match the LLVM version string because it was suffixed
with "svn" - i.e. "3.5.2svn".

Added the optional "svn" suffix to the CMake regex to fix this.

cmake/find_llvm.cmake

@@ -65,7 +65,7 @@ else()
  # Get LLVM version
  _run_llvm_config(LLVM_PACKAGE_VERSION "--version")
  # Try x.y.z patern
- set(_llvm_version_regex "^([0-9]+)\\.([0-9]+)\\.([0-9]+)$")
+ set(_llvm_version_regex "^([0-9]+)\\.([0-9]+)\\.([0-9]+)(svn)?$")
  if ("${LLVM_PACKAGE_VERSION}" MATCHES "${_llvm_version_regex}")
  string(REGEX REPLACE
  "${_llvm_version_regex}"