zircon: the type of zx_handle_t is now unsigned
zircon: the type of zx_handle_t is now unsigned

This is a kernel ABI change that landed today. I noticed some other ABI
issues and have left a note to cleanup once they are better defined.

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