According to POSIX.1 all error codes have to be distinct - with
the exception for EAGAIN and EWOULDBLOCK. Other libcs including
eglibc and newlib define EWOULDBLOCK as an alias for EAGAIN and
some software including OpenTTD expect this behavior.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
..and allow implicit creation of KResult and KResultOr from ErrnoCode.
This means that kernel functions that return those types can finally
do "return EINVAL;" and it will just work.
There's a handful of functions that still deal with signed integers
that should be converted to return KResults.
