Add syscall annotations for unimplemented syscalls

Added syscall annotations for unimplemented syscalls for later generation into
reference docs. Annotations are of the form:
@Syscall(<name>, <key:value>, ...)

Supported args and values are:

- arg: A syscall option. This entry only applies to the syscall when given this
       option.
- support: Indicates support level
  - UNIMPLEMENTED: Unimplemented (implies returns:ENOSYS)
  - PARTIAL: Partial support. Details should be provided in note.
  - FULL: Full support
- returns: Indicates a known return value. Values are
           syscall errors. This is treated as a string so you can use something
           like "returns:EPERM or ENOSYS".
- issue: A Github issue number.
- note: A note

Example:
// @Syscall(mmap, arg:MAP_PRIVATE, support:FULL, note:Private memory fully supported)
// @Syscall(mmap, arg:MAP_SHARED, support:UNIMPLEMENTED, issue:123, note:Shared memory not supported)
// @Syscall(setxattr, returns:ENOTSUP, note:Requires file system support)

Annotations should be placed as close to their implementation as possible
(preferrably as part of a supporting function's Godoc) and should be updated as
syscall support changes.

PiperOrigin-RevId: 241697482
Change-Id: I7a846135db124e1271dc5057d788cba82ca312d4

0 files changed, 0 insertions, 0 deletions