raw: Make compatible with LibRaw 0.21
imgdata.rawparams is split from imgdata.params
https://github.com/LibRaw/LibRaw/blob/637b935bef/Changelog.txt#L49
LibRaw 0.21 isn't released yet so might want to wait to merge this.
I have compiled with "LibRaw 202101 snapshot" and used to open raw files.