Do not silently truncate offsets for `read_at`/`write_at` on emscripten
Do not silently truncate offsets for `read_at`/`write_at` on emscripten

Generate an IO error if the offset is out of bounds for the system call.

graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,GBGamer/rust