Log Message:
xf86-video-intel: fix a segfault w/ clang & update to git 20210115

pkgsrc changes:
- Apply patches for upstream issue 171:
  "xf86-video-intel: segfault when built with clang"
- Fix similar issues in some other places.

Upstream changes:
- sna: Always validate userptr upon creation
- sna/gen7: Avoid clear-residuals overhead on all gen7
- sna: Enable TearFree by default on recent HW
- sna: Defer fbGetWindowPixmap() for sna_composite
- Track ABI changes for ABI_VIDEODRV_VERSION 25.2
- sna/gen7: Prefer blitter for plain copies on Haswell