Hash and detect savedata hashmode correctly.

Fixes Persona 1 savedata compatibility.
Check for missing SAVEDATA_PARAMS.
Merge pull request #6515 from unknownbrackets/savedata

Hash and detect savedata hashmode correctly
Qt: Modularise the settings file in to platforms with Arch / OS detection.
Qt: Buildfix Symbian. QT_ARCH='symbian', QMAKE_TARGET.arch=''
Qt: Buildfix ffmpeg search
Merge remote-tracking branch 'upstream/master' into fps2