Fix for PR15623. The patch eliminates unwanted ProgramState checker data propagation...

Fix for PR15623. The patch eliminates unwanted ProgramState checker data propagation from an operand of the logical operation to operation result.
The patch also simplifies an assume of a constraint of the form: "(exp comparison_op expr) != 0" to true into an assume of "exp comparison_op expr" to true. (And similarly, an assume of the form "(exp comparison_op expr) == 0" to true as an assume of exp comparison_op expr to false.) which improves precision overall.
https://reviews.llvm.org/D22862

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@290413 91177308-0d34-0410-b5e6-96231b3b80d8