llvm-slicer: first find slicing criterion and only after that assumptions
llvm-slicer: first find slicing criterion and only after that assumptions

in some cases we may not find the real slicing criterion, in which
case we would slice everything. Since we looked for the slicing criterion
and __VERIFIER_assume (klee_assume) at once, we still did not slice
all the module in the case that there was an assumption without
reachable slicing criterion

Signed-off-by: Marek Chalupa <a05df156a69ad59faa9af9b666ef78009594c145@gmail.com>

mchalupa/dg,mchalupa/dg,mchalupa/dg,mchalupa/dg