CodeGen: Refactor RTTI emission

Let's not expose ABI specific minutia inside of CodeGenModule and Type.
Instead, let's abstract it through CXXABI.

This gets rid of:
CodeGenModule::getCompleteObjectLocator,
CodeGenModule::EmitFundamentalTypeDescriptor{s,},
CodeGenModule::getMSTypeDescriptor,
CodeGenModule::getMSCompleteObjectLocator,
CGCXXABI::shouldRTTIBeUnique,
CGCXXABI::classifyRTTIUniqueness.

CGRTTI was *almost* entirely centered around providing Itanium-style
RTTI information.  Instead of providing interfaces that only it
consumes, move it to the ItaniumCXXABI implementation file.  This allows
it to have access to Itanium-specific implementation details without
providing useless expansion points for the Microsoft ABI side.

Differential Revision: http://reviews.llvm.org/D4261
StaticAnalyzer: Silence a warning

ExprEngine wasn't ready for SEHLeaveStmtClass.  Handle it like all the
other SEH constructs by aborting.