[scrapers] Support XSLT transforms (XML->XML) in the scrapers
cosmetic: indenting
[sorting] don't apply airdate when sorting by year if an empty airdate is specified. fixes #14276
- don't build xsltproc - it pulls in a lot of dependencies which are not available for rbpi (and so linker would try to link in x86 libs found in the system - which fails for arm linkage)
- force our libxml2 - fixes compilation on rbpi
Merge pull request #3758 from jmarshallnz/xslt_scraper

XSLT support in scrapers
Merge pull request #3889 from jmarshallnz/fix_sortlabel_year

[sorting] don't apply airdate when sorting by year if airdate is empty.
[WIN32] changed: used repackaged libxslt and libxml2. No need for the packaging scripts (thanks karlson2k)
videoplayer: adapt lateness detection and dropping to buffering
video player: present correct pts to user for a/v sync (after buffering in renderer)
videoplayer: some rework and documentation
renderer: bump buffers to 5
videoplayer: update frametime, it might change due to fps detection
videoplayer: give streams with invalid fps a chance for fps detection
dvdplayer: allow rewinding at end of stream, do a seek after rewind
X11: ditch SDL for video and window events
X11: Add xbmc icon
X11: add SDL joystick until we have a better solution
X11: factor out code handling device reset notification
X11: move xrandr events to WinEventsX11