Introduce basic support for dependent types, type-dependent

expressions, and value-dependent expressions. This permits us to parse
some template definitions.

This is not a complete solution; we're missing type- and
value-dependent computations for most of the expression types, and
we're missing checks for dependent types and type-dependent
expressions throughout Sema.

llvm-svn: 60615

clang/lib/AST/StmtIterator.cpp

@@ -16,6 +16,8 @@
 
 using namespace clang;
 
+// FIXME: Add support for dependent-sized array types in C++?
+// Does it even make sense to build a CFG for an uninstantiated template?
 static inline VariableArrayType* FindVA(Type* t) {
   while (ArrayType* vt = dyn_cast<ArrayType>(t)) {
     if (VariableArrayType* vat = dyn_cast<VariableArrayType>(vt))