BF: tools/dtime to handle log line having non-increment timestamp

Apparently can happen, likely due to multithreading and different threads
doing their own timestamping.  Interestingly Python seems to not handle
negative time delta "intuitively":

    (Pdb) p t
    datetime.datetime(2024, 5, 14, 19, 39, 12, 800000)
    (Pdb) p prevt
    datetime.datetime(2024, 5, 14, 19, 39, 12, 801000)
    (Pdb) p t - prevt
    datetime.timedelta(days=-1, seconds=86399, microseconds=999000)
    *(Pdb) p prevt -t
    datetime.timedelta(microseconds=1000)

but since python 2.7 there is "total_seconds" which is behaving as desired and
anyways we need those, so we can just use and thus operate correctly also
whenever crossing some days boundary (hopefully never).

tools/dtime

@@ -15,6 +15,7 @@ reg = re.compile('^\d{4}-\d{2}-\d{1,2} \d{1,2}:\d{1,2}:\d{1,2},\d{1,3}')
 prevt = None
 maxl = 0
 prevl = None
+warned_negative = False
 
 if len(sys.argv) <= 1:
     in_ = sys.stdin
@@ -30,7 +31,14 @@ for l in in_:
         t = datetime.strptime(l[:end], '%Y-%m-%d %H:%M:%S,%f')
         if prevt is not None:
             dt = t - prevt
-            ms = dt.microseconds // 1000 + dt.seconds*1000
+            secs = dt.total_seconds()
+            # negative dt has very weird form of -1 day + huge number of seconds
+            if secs < 0:
+                if not warned_negative:
+                    sys.stderr.write(f"Negative delta of {secs} seconds detected.  Might be due to threading etc\n")
+                    warned_negative = True
+
+            ms = secs * 1000
             dtstr = ("%5d" % ms if ms else '    0')
 
             maxl = max(maxl, len(dtstr))