Update defaults for variability of pointed-to types.

Now, if rate qualifiers aren't used to specify otherwise, varying
pointers point to uniform types by default.  As before, uniform
pointers point to varying types by default.

   float *foo;  // varying pointer to uniform float
   float * uniform foo;  // uniform pointer to varying float

These defaults seem to require the least amount of explicit
uniform/varying qualifiers for most common cases, though TBD if it
would be easier to have a single rule that e.g. the pointed-to type
is always uniform by default.

decl.cpp

@@ -408,7 +408,11 @@ Declarator::GetType(const Type *base, DeclSpecs *ds) const {
                     return NULL;
                 }
 
-                sym->type = PointerType::GetUniform(at->GetElementType());
+                const Type *targetType = at->GetElementType();
+                targetType = 
+                    targetType->ResolveUnboundVariability(Type::Varying);
+                sym->type = PointerType::GetUniform(targetType);
+
                 // Make sure there are no unsized arrays (other than the
                 // first dimension) in function parameter lists.
                 at = dynamic_cast<const ArrayType *>(at->GetElementType());