Misc Fixes II

[fabianbs96]

Again some smaller changes that now include:

• Fix an endless recursion in ConstantEdgeFunction::join
• Add const functions in psr::Table to make SolverResults const-correct (not silently adding default constructed entries to the underlying table when just calling resultAt)
• Add ctor overload to LLVMProjectIRDB that takes a llvm::MemoryBufferRef. Useful if your application needs to do some computations on the raw IR data before parsing it (e.g. calculating some hash-code, etc.)
• Add a utility hms to support printing time-durations. Useful if you want to benchmark some analyses

[MMory]

thanks a lot, looks good!