util.c: fix _WIN32 port of strptime (#3071)

In windows, time_t is a signed 32-bit integer type, so TIME_MAX needs to
be declared as INT32_MAX instead of INT64_MAX.

Also bump NetBSD's strptime to revision 1.65 from 1.63 to fix undefined
behaviour (signed integer overflow) bugs.

Related NetBSD problem report:
https://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=58041

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

I declared the d variable as  time_t  instead of as  unsigned  to ensure
that the signedness/size of  TIME_MAX-d  in the  sse > TIME_MAX-d check
is always correct, and to prevent -Wsign-compare warnings from
triggering in the windows build.

src/util.c

@@ -818,40 +818,47 @@ again:		switch (c = *fmt++) {
             LEGAL_ALT(ALT_O);
             continue;
 
-#ifndef TIME_MAX
-#define TIME_MAX	INT64_MAX
+        case 's': {     /* seconds since the epoch */
+#ifdef _WIN32
+            const time_t TIME_MAX = INT32_MAX;
+#else
+            const time_t TIME_MAX = INT64_MAX;
 #endif
-        case 's':	/* seconds since the epoch */
-            {
-                time_t sse = 0;
-                uint64_t rulim = TIME_MAX;
+            time_t sse;
+            time_t d;
+
+            if (*bp < '0' || *bp > '9') {
+                bp = NULL;
+                continue;
+            }
 
-                if (*bp < '0' || *bp > '9') {
+            sse = *bp++ - '0';
+            while (*bp >= '0' && *bp <= '9') {
+                d = *bp++ - '0';
+                if (sse > TIME_MAX/10) {
                     bp = NULL;
-                    continue;
+                    break;
                 }
-
-                do {
-                    sse *= 10;
-                    sse += *bp++ - '0';
-                    rulim /= 10;
-                } while ((sse * 10 <= TIME_MAX) &&
-                     rulim && *bp >= '0' && *bp <= '9');
-
-                if (sse < 0 || (uint64_t)sse > TIME_MAX) {
+                sse *= 10;
+                if (sse > TIME_MAX - d) {
                     bp = NULL;
-                    continue;
+                    break;
                 }
+                sse += d;
+            }
+            if (bp == NULL)
+                continue;
+
 #ifdef _WIN32
-                if (localtime_s(tm, &sse) == 0)
+            if (localtime_s(tm, &sse))
 #else
-                if (localtime_r(&sse, tm))
+            if (localtime_r(&sse, tm) == NULL)
 #endif
-                    state |= S_YDAY | S_WDAY | S_MON | S_MDAY | S_YEAR;
-                else
-                    bp = NULL;
-            }
+                bp = NULL;
+            else
+                state |= S_YDAY | S_WDAY | S_MON | S_MDAY | S_YEAR;
             continue;
+            }
 
         case 'U':	/* The week of year, beginning on sunday. */
         case 'W':	/* The week of year, beginning on monday. */