Fix min/max on MSVC

fix #1578

test/beast/core.cpp

@@ -7,5 +7,12 @@
 // Official repository: https://github.com/boostorg/beast
 //
 
+// If including Windows.h generates errors, it
+// means that min/max macros are being substituted.
+#ifdef _MSC_VER
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#endif
+
 // Test that header file is self-contained.
 #include <boost/beast/core.hpp>

test/beast/http.cpp

@@ -7,5 +7,12 @@
 // Official repository: https://github.com/boostorg/beast
 //
 
+// If including Windows.h generates errors, it
+// means that min/max macros are being substituted.
+#ifdef _MSC_VER
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#endif
+
 // Test that header file is self-contained.
 #include <boost/beast/http.hpp>

test/beast/ssl.cpp

@@ -7,5 +7,12 @@
 // Official repository: https://github.com/boostorg/beast
 //
 
+// If including Windows.h generates errors, it
+// means that min/max macros are being substituted.
+#ifdef _MSC_VER
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#endif
+
 // Test that header file is self-contained.
 #include <boost/beast/ssl.hpp>

test/beast/version.cpp

@@ -7,5 +7,12 @@
 // Official repository: https://github.com/boostorg/beast
 //
 
+// If including Windows.h generates errors, it
+// means that min/max macros are being substituted.
+#ifdef _MSC_VER
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#endif
+
 // Test that header file is self-contained.
 #include <boost/beast/version.hpp>

test/beast/websocket.cpp

@@ -7,5 +7,12 @@
 // Official repository: https://github.com/boostorg/beast
 //
 
+// If including Windows.h generates errors, it
+// means that min/max macros are being substituted.
+#ifdef _MSC_VER
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#endif
+
 // Test that header file is self-contained.
 #include <boost/beast/websocket.hpp>

test/beast/zlib.cpp

@@ -7,5 +7,12 @@
 // Official repository: https://github.com/boostorg/beast
 //
 
+// If including Windows.h generates errors, it
+// means that min/max macros are being substituted.
+#ifdef _MSC_VER
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#endif
+
 // Test that header file is self-contained.
 #include <boost/beast/zlib.hpp>