<rdar://problem/10796651> Introduce configuration macros into module maps.

Configuration macros are macros that are intended to alter how a
module works, such that we need to build different module variants
for different values of these macros. A module can declare its
configuration macros, in which case we will complain if the definition
of a configation macro on the command line (or lack thereof) differs
from the current preprocessor state at the point where the module is
imported. This should eliminate some surprises when enabling modules,
because "#define CONFIG_MACRO ..." followed by "#include
<module/header.h>" would silently ignore the CONFIG_MACRO setting. At
least it will no longer be silent about it.

Configuration macros are eventually intended to help reduce the number
of module variants that need to be built. When the list of
configuration macros for a module is exhaustive, we only need to
consider the settings for those macros when building/finding the
module, which can help isolate modules for various project-specific -D
flags that should never affect how modules are build (but currently do).



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177466 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer] Break cycles (optionally) when trimming an ExplodedGraph.

Having a trimmed graph with no cycles (a DAG) is much more convenient for
trying to find shortest paths, which is exactly what BugReporter needs to do.

Part of the performance work for <rdar://problem/13433687>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177468 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer] Re-apply "Do part of the work to find shortest bug paths up front".

With the assurance that the trimmed graph does not contain cycles,
this patch is safe (with a few tweaks), and provides the performance
boost it was intended to.

Part of performance work for <rdar://problem/13433687>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177469 91177308-0d34-0410-b5e6-96231b3b80d8