The ELAST macro is used on many systems to refer to the largest possible
valid errno value. LLVM's libc++ uses errno values of ELAST+1 and
ELAST+2 internally, and defines an arbitrary fallback value for
platforms which don't have the macro. This means that it's possible for
their internal errno numbers could coincide with values we actually use,
which would be a very bad thing.
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.
