Adjust booster to LLVM API (rename munmap function)

[jberthold]

The llvm-backend has added a function kllvm_reset_munmap_all_arenas to their C API.
While waiting for the respective LLVM backend release to succeed and reach K, we merged a hotfix which uses the internal reset_munmap_all_arenas instead. The name and kllvm-c.h header file should be adjusted once the K dependency is ready for it.

Originally posted by @jberthold in #4115 (comment)