New c64 sid (siddec) plugin using sidplayfp library

Implementation: GitHub - kilikali-nc/gst-siddecfp

siddecfp fixes some problems with current siddec plugin/library. playsidfp library also contains original resid implementation and it is selectable by properties. New residfp is default and it uses floating points.

So reason to mplement sidplayfp-plugin is still developed. sidplay is not. + most tunes works with fp version unlike original one,

Original siddec supports only PSID files, siddecfp supports both PSID and RSID files. I think GStreamer has bug which recognize PSID files as x-sid. I think it should be x-psid. Some RSIDs require rom files, check README.md n perository. SID-files are really piece of software so requirements might be different for different songs.

Anyway added also untested patch for RSID-files which should be recognized as x-rsid files. I lost my original patch and made new one.

gst-app in repository adds “hack” to override GStreamers original type-find with own.
siddecfp fixes some problems with current siddec library. playsidfp library also contains original resid implementation and it is selectable by properties. New residfp is default and it uses floating points.

I also had some siddec patches, but also lost those.

Main concern is it OK to use GByteArray to pass 4-8kB of data as property.

Any other comments?