Fix symbol visibility across build triplets.
Submitted upstream in https://github.com/P-H-C/phc-winner-argon2/pull/262


diff --git a/include/argon2.h b/include/argon2.h
index 3980bb3..2738960 100644
--- a/include/argon2.h
+++ b/include/argon2.h
@@ -27,15 +27,29 @@ extern "C" {
 #endif
 
 /* Symbols visibility control */
-#ifdef A2_VISCTL
-#define ARGON2_PUBLIC __attribute__((visibility("default")))
-#define ARGON2_LOCAL __attribute__ ((visibility ("hidden")))
-#elif _MSC_VER
-#define ARGON2_PUBLIC __declspec(dllexport)
-#define ARGON2_LOCAL
+#if defined(_WIN32)
+  #if defined(A2_VISCTL)
+    #if defined(_MSC_VER) || defined(__MINGW32__)
+      #define ARGON2_PUBLIC __declspec(dllexport)
+    #else
+      #define ARGON2_PUBLIC __attribute__ ((dllexport))
+    #endif
+  #else
+    #if defined(_MSC_VER) || defined(__MINGW32__)
+      #define ARGON2_PUBLIC __declspec(dllimport)
+    #else
+      #define ARGON2_PUBLIC /*__attribute__ ((dllimport))*/
+    #endif
+  #endif
+  #define ARGON2_LOCAL
 #else
-#define ARGON2_PUBLIC
-#define ARGON2_LOCAL
+  #if defined(A2_VISCTL)
+    #define ARGON2_PUBLIC __attribute__ ((visibility ("default")))
+    #define ARGON2_LOCAL  __attribute__ ((visibility ("hidden")))
+  #else
+    #define ARGON2_PUBLIC
+    #define ARGON2_LOCAL
+  #endif
 #endif
 
 /*