Libraries/LibCpp: Add parser test for out-of-line function definitions

Userland/Libraries/LibCpp/Tests/parser/out-of-line.ast

@@ -0,0 +1,21 @@
+TranslationUnit[2:0->9:0]
+  StructOrClassDeclaration[2:6->7:0]
+  A
+    FunctionDeclaration[4:4->4:14]
+      NamedType[4:4->4:7]
+        bool
+      foo
+      (
+      )
+  FunctionDeclaration[7:0->9:0]
+    NamedType[7:0->7:3]
+      bool
+    A::foo
+    (
+    )
+    FunctionDefinition[7:14->9:0]
+    {
+      ReturnStatement[8:4->8:15]
+        BooleanLiteral[8:11->8:14]
+          true
+    }

Userland/Libraries/LibCpp/Tests/parser/out-of-line.cpp

@@ -0,0 +1,10 @@
+
+
+class A
+{
+    bool foo();
+};
+
+bool A::foo() {
+    return true;
+}