mythccextractor srt subtitle display times too short

On a UK DVB recording mythccextractor is producing an srt file with
subtitle display times too short to read. The utility telxcc v2.2.0
does not have this issue. Both utilities extract the same text
page 0x888 subtitle track.

## Example of a telxcc srt file:

1
00:00:02,560 --> 00:00:07,400
Everything around us is shaped
by metals. Everything.

2
00:00:07,440 --> 00:00:12,080
It's that step-by-step understanding
of the internal structure of metals,

3
00:00:12,120 --> 00:00:14,120
the secret world
of the metal crystal,

4
00:00:14,160 --> 00:00:16,640
that's been a huge
intellectual achievement.


## Example of a mythccextractor srt file:

1
00:00:02,360 --> 00:00:03,110
Everything around us is shaped
by metals. Everything.

2
00:00:07,200 --> 00:00:07,950
It's that step-by-step understanding
of the internal structure of metals,

3
00:00:11,960 --> 00:00:12,710
the secret world
of the metal crystal,

4
00:00:13,960 --> 00:00:14,710
that's been a huge
intellectual achievement.