Log Message:
tex-graphics-def{,-doc}: update to 2021

- Disable use of new (x)dvipdfmx color stacks pending further testing
- Correct error given if .gz files are given as graphics with (x)dvipdfmx

Further work to support multiple color stacks in (x)dvipdfmx

This update allows use of new colour stacks in dvipdfmx/XeTeX.