[analyzer] MinComplexityConstraint now early exits and only does one macro stack lookup

Summary:
This patch contains performance improvements for the `MinComplexityConstraint`. It reduces the constraint time when running on the SQLite codebase by around 43% (from 0.085s down to 0.049s).

The patch is essentially doing two things:

* It introduces a possibility for the complexity value to early exit when reaching the limit we were checking for. This means that once we noticed that the current clone is larger than the limit the user has set, we instantly exit and no longer traverse the tree or do further expensive lookups in the macro stack.

* It also removes half of the macro stack lookups we do so far. Previously we always checked the start and the end location of a Stmt for macros, which was only a middle way between checking all locations of the Stmt and just checking one location. In practice I rarely found cases where it really matters if we check start/end or just the start of a statement as code with lots of macros that somehow just produce half a statement are very rare.

Reviewers: NoQ

Subscribers: cfe-commits, xazax.hun, v.g.vassilev

Differential Revision: https://reviews.llvm.org/D34361

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@312440 91177308-0d34-0410-b5e6-96231b3b80d8