- switch to llvm 9
- Update to version 2.0+20191031:
* Executor: fix missing default case in switch instruction
* enable testing for LLVM 9.0
* LLVM 9.0: fourth parameter for @llvm.objectsize()
* klee-libc: add bcmp
* support compilation against LLVM 9.0
* [klee-replay] Fix relative executable paths
* ExecutorTimers: refactor and move to support lib
* ExecutorTimers: remove signalling, fix endless looping fork
* Executor.h: remove defined functions without implementation
* test/Expr/Evaluate2.kquery: add link to issue
* fix: make llvm 7.1 known
* test/Feature/SolverTimeout.c: re-enable for Z3
* test/lit.cfg: test if current version is known
* test/lit.cfg: use lit_config instead of lit
* Do not use klee_range() in regression/2014-09-13-debug-info.c test, as it is incompatible with klee_prefer_cex. Fixes https://github.com/klee/klee/issues/1161