Add dap::initialize() and terminate() functions

Can be used to explicitly control when the TypeInfo static initializers / destructors are called.
Usually not needed.

Issue: #40

include/dap/dap.h

@@ -0,0 +1,35 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef dap_dap_h
+#define dap_dap_h
+
+namespace dap {
+
+// Explicit library initialization and termination functions.
+//
+// cppdap automatically initializes and terminates its internal state using lazy
+// static initialization, and so will usually work fine without explicit calls
+// to these functions.
+// However, if you use cppdap types in global state, you may need to call these
+// functions to ensure that cppdap is not uninitialized before the last usage.
+//
+// Each call to initialize() must have a corresponding call to terminate().
+// It is undefined behaviour to call initialize() after terminate().
+void initialize();
+void terminate();
+
+}  // namespace dap
+
+#endif  // dap_dap_h