Added prototype for _strtoi64().

/* For MSVC7 we can use _strtoi64() which seems to be a strtoll() clone */

#if defined(_MSC_VER) && (_MSC_VER >= 1300)

_CRTIMP __int64 __cdecl _strtoi64(const char *, char **, int);  /* in <crt/stdlib.h> */

#define curlx_strtoofft _strtoi64

#else /* MSVC7 or later */

curl_off_t curlx_strtoll(const char *nptr, char **endptr, int base);