minor improvements to dvd seeking.

[skamithi]

in DVDRingBuffer::GetReadPosition, sometimes dvdnav_get_position fails. this affects seeking. e.g, you are ffw and it just jumps to the beginning of the feature. trying a couple of things to see how to minimize the effects of this condition.

[skamithi]

if dvdnav_get_pos fails the first time, have some delay then try again. if its still wrong..oh well. seems to work most of the time. still testing.

[skamithi]

(In [10048]) Closes #1827. minor improvements in dvd ff/rew.

[skamithi]

if getreadposition returns 0 tell decoderbase to use the current framesplayed.

[skamithi]

some more improvements in dvd seeking.

• stop been in rewind mode when at the beginning of the dvd
• prevent dvd from jumping back to the beginning of the dvd when leaving rewind mode
• prevent dorewind() or doforward() when leaving rewind mode while watching a dvd.

still testing the additional patch.

[skamithi]

(In [10252]) Refs #1827. internal dvd player ff/rew improvements.

[skamithi]

seekrwnd and seekffwd using internal dvd player doesn't work. working on a fix.

[skamithi]

(In [10278]) Refs #1827. one change in [10252] broke skip ahead/behind for the internal dvd player. problem found by john poet.

[skamithi]

noticed that when DVDRB::Seek is run and it fails, waiting til the next cell change makes it work again.

[skamithi]

allowing jumping to the next title when you reach the end of the title. previous restriction was that jumping is only allowed if chapters < 3

[skamithi]

dvd_title jumping patch will allow you to jump to the next title even if the title is a dvd menu. i cannot find a function that allows me to look ahead and see if the next title in the chain is a dvd menu or not.

if i find it or get time to code it, i'll add it.

[skamithi]

(In [10306]) Refs #1827. internal dvd player seeking changes. allow title jumping if current number of chapters in title > 2. also, added minor changes to the DVDRB::Seek function.