ThirdParty: Add optional-lite polyfill

Thanks to all who have made contributions to
https://github.com/martinmoene/optional-lite

third-party/optional-lite/extra/gdb/nonstd_optional_printer.py

@@ -0,0 +1,26 @@
+# gdb pretty-printer contributed by @bas524, Alexander B.
+# 
+# register with:
+#   libstdcxx_printer.add_version('nonstd::optional_lite::', 'optional', NonStdOptionalPrinter)
+
+class NonStdOptionalPrinter(SingleObjContainerPrinter):
+    "Print a nonstd::optional"
+
+    def __init__ (self, typename, val):
+        alternatives = get_template_arg_list(val.type)
+        valtype = self._recognize (val.type.template_argument(0))
+        self.typename = strip_versioned_namespace(typename)
+        self.typename = re.sub('^nonstd::(optional_lite::|)(optional::|)(.*)', r'nonstd::\1\3<%s>' % valtype, self.typename, 1)
+        self.val = val
+        self.contained_type = alternatives[0]
+        addr = val['contained']['data']['__data'].address
+        contained_value = addr.cast(self.contained_type.pointer()).dereference()
+        visualizer = gdb.default_visualizer (contained_value)
+        super (NonStdOptionalPrinter, self).__init__ (contained_value, visualizer)
+
+    def to_string (self):
+        if self.contained_value is None:
+            return "%s [no contained value]" % self.typename
+        if self.visualizer:
+            return "%s containing %s" % (self.typename, self.visualizer.to_string())
+        return self.typename