Revert "THRIFT-2045: C++ compiler warning and build cleanup"

This reverts commit 282e440c6de219b7b8f32b01cc7eb599f534f33f.

This change had unintended autoconf side effects.
diff --git a/compiler/cpp/src/platform.h b/compiler/cpp/src/platform.h
index 7eb891d..04f04c7 100644
--- a/compiler/cpp/src/platform.h
+++ b/compiler/cpp/src/platform.h
@@ -22,11 +22,7 @@
  * is different for the non-POSIX MinGW
  */
 
-#ifdef HAVE_CONFIG_H
-#include "config.h"
-#endif
-
-#ifdef _WIN32
+#ifdef MINGW
 #include <direct.h>
 #include <io.h>
 #else
@@ -34,14 +30,8 @@
 #include <sys/stat.h>
 #endif
 
-#ifdef _WIN32
+#if defined MINGW
 #define MKDIR(x) mkdir(x)
 #else
 #define MKDIR(x) mkdir(x, S_IRWXU | S_IRWXG | S_IRWXO)
 #endif
-
-#ifdef PATH_MAX
-#define THRIFT_PATH_MAX PATH_MAX
-#else
-#define THRIFT_PATH_MAX MAX_PATH
-#endif