Fix linker definition clashes between libargon2 and libsodium on Windows

cmake/FindArgon2.cmake

@@ -14,7 +14,20 @@
 #  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 find_path(ARGON2_INCLUDE_DIR argon2.h)
+if (MINGW)
+  # find static library on Windows, and redefine used symbols to
+  # avoid definition name conflicts with libsodium
+  find_library(ARGON2_SYS_LIBRARIES libargon2.a)
+  message(STATUS "Patching libargon2...")
+  execute_process(COMMAND objcopy
+              --redefine-sym argon2_hash=libargon2_argon2_hash
+              --redefine-sym argon2_error_message=libargon2_argon2_error_message
+              ${ARGON2_SYS_LIBRARIES} ${CMAKE_BINARY_DIR}/libargon2_patched.a
+          WORKING_DIRECTORY ${CMAKE_BINARY_DIR})
+  find_library(ARGON2_LIBRARIES libargon2_patched.a PATHS ${CMAKE_BINARY_DIR} NO_DEFAULT_PATH)
+else()
   find_library(ARGON2_LIBRARIES argon2)
+endif()
 mark_as_advanced(ARGON2_LIBRARIES ARGON2_INCLUDE_DIR)
 
 include(FindPackageHandleStandardArgs)

src/crypto/argon2/argon2.h

@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2018 KeePassXC Team <team@keepassxc.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 or (at your option)
+ * version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef KEEPASSXC_CRYPTO_ARGON2_H
+#define KEEPASSXC_CRYPTO_ARGON2_H
+
+/*
+    Argon2 wrapper header with redefined symbols to be used with the
+    patched libargon2 binary which is generated by the build system.
+    This is to avoid link-time definition clashes with libsodium on Windows.
+ */
+
+#ifdef Q_OS_WIN
+#define argon2_hash libargon2_argon2_hash
+#define argon2_error_message libargon2_argon2_error_message
+#endif
+
+#include <argon2.h>
+
+#endif //KEEPASSXC_CRYPTO_ARGON2_H

src/crypto/kdf/Argon2Kdf.cpp

@@ -18,8 +18,8 @@
 #include "Argon2Kdf.h"
 
 #include <QtConcurrent>
-#include <argon2.h>
 
+#include "crypto/argon2/argon2.h"
 #include "format/KeePass2.h"
 
 /**