Revert "[analyzer] Do part of the work to find shortest bug paths up front."

The whole reason we were doing a BFS in the first place is because an
ExplodedGraph can have cycles. Unfortunately, my removeErrorNode "update"
doesn't work at all if there are cycles.

I'd still like to be able to avoid doing the BFS every time, but I'll come
back to it later.

This reverts r177353 / 481fa5071c203bc8ba4f88d929780f8d0f8837ba.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177448 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer] Add a test case for diagnostic suppression on a graph with cycles.

(see previous commit)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177449 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer] Do not believe lazy binding when symbolic region types do not match

This fixes a crash when analyzing LLVM that was exposed by r177220 (modeling of
trivial copy/move assignment operators).

When we look up a lazy binding for “Builder”, we see the direct binding of Loc at offset 0.
Previously, we believed the binding, which led to a crash. Now, we do not believe it as
the types do not match.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177453 91177308-0d34-0410-b5e6-96231b3b80d8