move from ssize_t to the C standard based ptrdiff_t

Author: Bas Alberts

extensions/autolink.c

@@ -2,21 +2,14 @@
 #include <parser.h>
 #include <string.h>
 #include <utf8.h>
+#include <stddef.h>
 
 #if defined(_WIN32)
 #define strncasecmp _strnicmp
 #else
 #include <strings.h>
 #endif
 
-// for ssize_t
-#ifdef _MSC_VER
-#include <BaseTsd.h>
-typedef SSIZE_T ssize_t;
-#else
-#include <unistd.h>
-#endif
-
 static int is_valid_hostchar(const uint8_t *link, size_t link_len) {
   int32_t ch;
   int r = cmark_utf8proc_iterate(link, (bufsize_t)link_len, &ch);
@@ -314,7 +307,7 @@ static bool validate_protocol(char protocol[], uint8_t *data, size_t rewind, siz
     return true;
   }
 
-  char prev_char = data[-((ssize_t)rewind) - len - 1];
+  char prev_char = data[-((ptrdiff_t)rewind) - len - 1];
 
   // Make sure the character before the protocol is non-alphanumeric
   return !cmark_isalnum(prev_char);