Add two constant definitions

This fixes compiler errors for vs 2008.

Change-Id: Ifaabb1c5e74fe6ede6dacf66ec3f634fecb556fd
diff --git a/vpx/vpx_integer.h b/vpx/vpx_integer.h
index 500f9b9..829c9d1 100644
--- a/vpx/vpx_integer.h
+++ b/vpx/vpx_integer.h
@@ -37,6 +37,8 @@
 typedef signed __int64   int64_t;
 typedef unsigned __int64 uint64_t;
 #define INT64_MAX _I64_MAX
+#define INT32_MAX _I32_MAX
+#define INT32_MIN _I32_MIN
 #define INT16_MAX _I16_MAX
 #define INT16_MIN _I16_MIN
 #endif