Hide key template instances behind factory functions.

And provide a separate "module library"
Update testing scripts.

module/regex_create_char.cpp

@@ -0,0 +1,31 @@
+
+#if defined(__cpp_lib_modules) || (defined(_MSC_FULL_VER) && (_MSC_FULL_VER >= 193933523))
+#define BOOST_REGEX_USE_STD_MODULE
+#endif
+
+#ifndef BOOST_REGEX_USE_STD_MODULE
+module;
+
+#include <memory>
+
+#endif
+
+#ifndef BOOST_REGEX_DETAIL_NS
+#define BOOST_REGEX_DETAIL_NS re_detail_600
+#endif
+
+module boost.regex;
+
+#ifdef BOOST_REGEX_USE_STD_MODULE
+import std;
+#endif
+
+namespace boost::detail {
+
+   std::shared_ptr<BOOST_REGEX_DETAIL_NS::basic_regex_implementation<char, basic_regex<char>::traits_type> >
+      create_implemenation(const char* p1, const char* p2, basic_regex<char>::flag_type f, std::shared_ptr<boost::regex_traits_wrapper<basic_regex<char>::traits_type> > ptraits)
+   {
+      return create_implemenation<char, basic_regex<char>::flag_type, basic_regex<char>::traits_type>(p1, p2, f, ptraits);
+   }
+
+}