1.4.3
  - Major update in gifski rust library. This also required different
    threading implementation in the bindings.

0.8.7.1
  - Add workaround for compiling with old rustc compilers
  - Add workaround for linking error with experimental UCRT toolchain

0.8.7
  - CRAN insists that we override the standard cargo/rust behaviour which
    stores registry and crate data in ~/.cargo, because policy. So we now
    build with CARGO_HOME set to a temporary dir that is deleted afterwards.
    This probably makes this slower and more error prone, but I don't make
    these rules.

0.8.6
  - Update gifski crate to 0.8.6
  - save_gif() now properly closes graphics device when expr errors
  - More rubust C code to prevent segfaults on write errors
  - File paths are now converted to UTF-8 as described in gifski.h
