Fix: The window title wasn't displayed when "Display full path" option was used.

This option was broken after bd905fce40009a950c754486133ab89da2c9919d.

This commit fixes ticket #3394.
Fix: the window title was wrong in capture mode when "Display full path / file name" was used.
Cosmetics: Don't use "m_" prefix for function variables.
Use pipe:stdin instead of pipe:0 to get clearer OSD message and window title.
PlayerSeekbar: utilize last WM_MOUSEMOVE point

In mouse capture mode, and seek only if new x coordinate differs.
It fixes madVR with delayed seek option enabled seeking to the same
point repeatedly.
PlayerSeekbar: code refactoring follow-up

A few minor things I missed in 444d7e9
Modify goto subtitle behavior

Jump only if there's a subtitle present. Previously mpc-hc performed 5s
jump if there was no subtitle, even beyond the end of stream.
New "Jump to Beginning" command
Fix: the window title was wrong in DVD mode when "Display full path" was used.
WebServer: Add margin-top to seekbar.
VideoRenderers: Set backbuffer size to full virtual screen size when not in D3DFS.

No more need to reinitialize the renderer when changing displays and will allow you to render the video across multiple monitors.
DX9AllocatorPresenter: Reset the device when the present mode changes.

Do it after the desktop display mode has been changed. That covers the changes in virtual desktop size too.  The other renderers already do this.
AppSettings: Turn off "Reinitialize when changing displays" by default on Vista+.

It's no longer as important now that the backbuffer is large enough to cover the entire Desktop. It's still needed for VSync though, so keep it on by default on for XP.