util.c: fix _WIN32 port of strptime

In _WIN32 builds, TIME_MAX needs to be INT32_MAX.

Also fix UB-overflow/useless-check in BSD's strptime:
  (time_t_value * 10) < TIME_MAX  is always true since time_t is signed
and, if it is not optimised out, it causes a signed integer overflow
for input that start with a sequence of characters between
"922337203685477581" and "999999999999999999" (inclusive, 64-bit time_t)
that is unspecified in standard C.

Noticed thanks to a compiler warning in the windows build CI.

src/util.c

@@ -819,11 +819,15 @@ again:		switch (c = *fmt++) {
             continue;
 
 #ifndef TIME_MAX
+#ifdef _WIN32
+#define TIME_MAX	INT32_MAX
+#else
 #define TIME_MAX	INT64_MAX
+#endif
 #endif
         case 's':	/* seconds since the epoch */
             {
-                time_t sse = 0;
+                uint64_t sse = 0;
                 uint64_t rulim = TIME_MAX;
 
                 if (*bp < '0' || *bp > '9') {
@@ -835,17 +839,18 @@ again:		switch (c = *fmt++) {
                     sse *= 10;
                     sse += *bp++ - '0';
                     rulim /= 10;
-                } while ((sse * 10 <= TIME_MAX) &&
+                } while (sse * 10 <= TIME_MAX &&
                      rulim && *bp >= '0' && *bp <= '9');
 
-                if (sse < 0 || (uint64_t)sse > TIME_MAX) {
+                if (sse > TIME_MAX) {
                     bp = NULL;
                     continue;
                 }
+                time_t tsse = sse;
 #ifdef _WIN32
-                if (localtime_s(tm, &sse) == 0)
+                if (localtime_s(tm, &tsse) == 0)
 #else
-                if (localtime_r(&sse, tm))
+                if (localtime_r(&tsse, tm))
 #endif
                     state |= S_YDAY | S_WDAY | S_MON | S_MDAY | S_YEAR;
                 else