Merge pull request libretro#7156 from RetroSven/master

 push save state into background for cores that need the emulator to be running during serialization

Update to 1.7.3

win32_get_refresh_rate not available on Xbox

(XDK1) Set default assets dir too

Disable automatically add content by playlist by default

Update CHANGES.md

MSVC 2005 - buildfix

Update CHANGES.md

Merge pull request libretro#5315 from ensra/master

Fix db build

Bump up to 1.6.4