LCA improvements

[fabianbs96]

Several updates in the IDELinearConstantAnalysis

[pdschubert]

Thanks for the improvements. However, the unit tests cannot be build since a required operator== is missing:

-c ../unittests/PhasarLLVM/ControlFlow/LLVMBasedICFGGlobCtorDtorTest.cpp
In file included from ../unittests/PhasarLLVM/ControlFlow/LLVMBasedICFGGlobCtorDtorTest.cpp:10:
../external/googletest/googletest/include/gtest/gtest.h:1545:11: error: invalid operands to binary expression ('const int' and 'const psr::LatticeDomain<long>')
  if (lhs == rhs) {

[pdschubert]

I'm working on a fix.