Provide more control over automatic generation of docstrings (#486)

Added the docstring_options class, which gives global control over the generation of docstrings and function signatures.

tests/test_docstring_options.cpp

@@ -0,0 +1,53 @@
+/*
+    tests/test_docstring_options.cpp -- generation of docstrings and signatures
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#include "pybind11_tests.h"
+
+struct DocstringTestFoo {
+    int value;
+    void setValue(int v) { value = v; }
+    int getValue() const { return value; }
+};
+
+test_initializer docstring_generation([](py::module &m) {
+
+    {
+        py::options options;
+        options.disable_function_signatures();
+
+        m.def("test_function1", [](int, int) {}, py::arg("a"), py::arg("b"));
+        m.def("test_function2", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+
+        options.enable_function_signatures();
+
+        m.def("test_function3", [](int, int) {}, py::arg("a"), py::arg("b"));
+        m.def("test_function4", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+
+        options.disable_function_signatures().disable_user_defined_docstrings();
+
+        m.def("test_function5", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+
+        {
+            py::options nested_options;
+            nested_options.enable_user_defined_docstrings();
+            m.def("test_function6", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+        }
+    }
+
+    m.def("test_function7", [](int, int) {}, py::arg("a"), py::arg("b"), "A custom docstring");
+
+    {
+        py::options options;
+        options.disable_user_defined_docstrings();
+
+        py::class_<DocstringTestFoo>(m, "DocstringTestFoo", "This is a class docstring")
+            .def_property("value_prop", &DocstringTestFoo::getValue, &DocstringTestFoo::setValue, "This is a property docstring")
+        ;
+    }
+});