signed/unsigned fixes, and some other fixes

src/core/common.h

@@ -73,11 +73,16 @@ typedef int16_t int16;
 typedef uint32_t uint32;
 typedef int32_t int32;
 typedef uintptr_t uintptr;
+typedef intptr_t intptr;
 typedef uint64_t uint64;
 typedef int64_t int64;
 // hardcode ucs-2
 typedef uint16_t wchar;
 
+#if defined(_MSC_VER)
+typedef ptrdiff_t ssize_t;
+#endif
+
 #ifndef nil
 #define nil NULL
 #endif