Fix internal links (#255)

idioms/ctor.md

@@ -32,5 +32,5 @@ impl<T> Vec<T> {
 
 ## See also
 
-The [builder pattern](../patterns/builder.md) for constructing objects where
-there are multiple configurations.
+The [builder pattern](../patterns/creational/builder.md) for constructing objects
+where there are multiple configurations.

idioms/dtor-finally.md

@@ -87,4 +87,4 @@ resources in an unexpected state.
 
 ## See also
 
-[RAII](../patterns/RAII.md).
+[RAII guards](../patterns/behavioural/RAII.md).

idioms/on-stack-dyn-dispatch.md

@@ -84,7 +84,8 @@ Read`
 ## See also
 
 * [Finalisation in destructors](dtor-finally.md) and
-[RAII guards](../patterns/RAII.md) can benefit from tight control over lifetimes.
+[RAII guards](../patterns/behavioural/RAII.md) can benefit from tight control over
+lifetimes.
 * For conditionally filled `Option<&T>`s of (mutable) references, one can
 initialize an `Option<T>` directly and use its [`.as_ref()`] method to get an
 optional reference.