Add support for Microsoft's C++ stdlib (#133)

Add support for Microsoft's C++ stdlib

include/boost/predef/library/std.h

@@ -16,6 +16,7 @@ http://www.boost.org/LICENSE_1_0.txt)
 #include <boost/predef/library/std/libcomo.h>
 #include <boost/predef/library/std/modena.h>
 #include <boost/predef/library/std/msl.h>
+#include <boost/predef/library/std/msvc.h>
 #include <boost/predef/library/std/roguewave.h>
 #include <boost/predef/library/std/sgi.h>
 #include <boost/predef/library/std/stdcpp3.h>

include/boost/predef/library/std/msvc.h

@@ -0,0 +1,53 @@
+/*
+Copyright Henrik S. Gaßmann 2023
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE_1_0.txt or copy at
+http://www.boost.org/LICENSE_1_0.txt)
+*/
+
+#ifndef BOOST_PREDEF_LIBRARY_STD_MSVC_H
+#define BOOST_PREDEF_LIBRARY_STD_MSVC_H
+
+#include <boost/predef/library/std/_prefix.h>
+
+#include <boost/predef/version_number.h>
+#include <boost/predef/make.h>
+
+/* tag::reference[]
+= `BOOST_LIB_STD_MSVC`
+
+https://github.com/microsoft/STL[Microsoft's {CPP} Standard Library].
+If available version number as major, minor, and patch.
+The patch number is derived from `_MSVC_STL_UPDATE` by taking its five last
+digits (see below). This implies that pasting a `_MSVC_STL_UPDATE` value into
+`BOOST_VERSION_NUMBER` will produce a version number that is directly comparable
+to `BOOST_LIB_STD_MSVC`.
+
+[options="header"]
+|===
+| {predef_symbol} | {predef_version}
+
+| `+_MSVC_STL_VERSION+` | {predef_detection}
+
+| `+_MSVC_STL_VERSION+` | VV.R.0
+| `+_MSVC_STL_UPDATE+` | 00.0.0YYYMM
+|===
+*/ // end::reference[]
+
+#define BOOST_LIB_STD_MSVC BOOST_VERSION_NUMBER_NOT_AVAILABLE
+
+#if defined(_MSVC_STL_VERSION)
+#   undef BOOST_LIB_STD_MSVC
+#   define BOOST_LIB_STD_MSVC BOOST_PREDEF_MAKE_10_VVR_0PPPPP(_MSVC_STL_VERSION, _MSVC_STL_UPDATE)
+#endif
+
+#if BOOST_LIB_STD_MSVC
+#   define BOOST_LIB_STD_MSVC_AVAILABLE
+#endif
+
+#define BOOST_LIB_STD_MSVC_NAME "Microsoft stdlib"
+
+#endif
+
+#include <boost/predef/detail/test.h>
+BOOST_PREDEF_DECLARE_TEST(BOOST_LIB_STD_MSVC, BOOST_LIB_STD_MSVC_NAME)

include/boost/predef/make.h

@@ -106,6 +106,10 @@ Macros are:
 */ // end::reference[]
 #define BOOST_PREDEF_MAKE_10_VV00(V) BOOST_VERSION_NUMBER(((V)/100)%100,0,0)
 /* tag::reference[]
+* `BOOST_PREDEF_MAKE_10_VVR_0PPPPP(V, P)`, the second parameter specifies a year-month patch level with the first digit discarded
+*/ // end::reference[]
+#define BOOST_PREDEF_MAKE_10_VVR_0PPPPP(V, P) BOOST_VERSION_NUMBER(((V)/10)%100,(V)%10,(P)%100000)
+/* tag::reference[]
 * `BOOST_PREDEF_MAKE_10_VVRR(V)`
 */ // end::reference[]
 #define BOOST_PREDEF_MAKE_10_VVRR(V) BOOST_VERSION_NUMBER(((V)/100)%100,(V)%100,0)