Fix portability issues for building tests in MinGW

Author: ashtum

test/beast/core/file_test.hpp

@@ -16,7 +16,6 @@
 #include <boost/filesystem/path.hpp>
 #include <boost/filesystem/operations.hpp>
 #include <boost/filesystem/fstream.hpp>
-#include <fstream>
 #include <iterator>
 #include <string>
 #include <type_traits>
@@ -43,7 +42,7 @@ test_file()
     namespace fs = boost::filesystem;
 
     static constexpr
-#ifdef _WIN32
+#if defined(_WIN32) && !defined(__MINGW32__) && !defined(__MINGW64__)
     boost::winapi::WCHAR_ unicode_suffix[] = { 0xd83e, 0xdd84, 0x0000 }; // UTF-16-LE unicorn
 #else
     char                  unicode_suffix[] = { '\xf0', '\x9f', '\xa6', '\x84', '\x00' }; // UTF-8 unicorn
@@ -112,8 +111,8 @@ test_file()
         [](fs::path const& path)
         {
             // no exceptions - failure will result in an empty string
-            std::ifstream in;
-            in.open(path.native());
+            fs::ifstream in;
+            in.open(path);
             noskipws(in);
             auto s = std::string(
                 std::istream_iterator<char>(in),

test/beast/http/file_body.cpp

@@ -168,7 +168,7 @@ class file_body_test : public beast::unit_test::suite
             "0123456789"; // 40
         // create the temporary file
         {
-            std::ofstream fstemp(temp.path().native());
+            std::ofstream fstemp(temp.path().string());
             std::size_t written = 0;
             std::size_t to_write = 4097;
             while (written < to_write)
@@ -223,7 +223,7 @@ class file_body_test : public beast::unit_test::suite
                 "0123456789"; // 40
         // create the temporary file
         {
-            std::ofstream fstemp(temp.path().native());
+            std::ofstream fstemp(temp.path().string());
             std::size_t written = 0;
             std::size_t to_write = 2048;
             while (written < to_write)