Fix strict-alias warnings

[winterheart]

reinterpret_cast on pointers break strict-aliasing rule (-Wstrict-aliasing). Implemented internal function copy_reinterpret_cast that memcpy pointer into type, that can be converted to desired type.

Closes aseprite/aseprite#4413

I agree that my contributions are licensed under the MIT License.
You can find a copy of this license at https://opensource.org/licenses/MIT

[aseprite-bot]

clang-tidy review says "All clean, LGTM! 👍"

[dacap]

Thanks @winterheart, I've just tested and this change segfaults one of our userdata_codec.lua tests where these functions are used:

Testing scripts...
Running scripts/userdata_codec.lua
run-tests.sh: line 69:  1690 Segmentation fault      $ASEPRITE -b --script $script > $t/tmp 2>&1