Silence compiler warning about unused variable
Disable redefinition of functions
Fix test case to use llvm-link instead of llvm-ld
Silence warning of deprecated PathV1 usage
Link against shared library from LLVM correctly

Searching for the LLVM library was conducted in the Klee project.
This patch searches in the LLVM build directory.
Fix constness warnings issued by gcc 4.7
Fixed warning about unused variable