fs/AllocatedPath: add method Steal()

src/fs/AllocatedPath.hxx

@@ -169,6 +169,14 @@ public:
 		return *this;
 	}
 
+	/**
+	 * Allows the caller to "steal" the internal value by
+	 * providing a rvalue reference to the std::string attribute.
+	 */
+	std::string &&Steal() {
+		return std::move(value);
+	}
+
 	/**
 	 * Check if this is a "nulled" instance.  A "nulled" instance
 	 * must not be used.