`atomic-(add|sub)-fetch` not documented or indexed

[lizmat]

The title says it all.

[codesections]

It also looks like none of the atomic operators are documented in /language/operators. Here's the full list (taken from /language/unicode_ascii in case anyone feels like taking a crack at adding them)

  ⚛=  | atomic-assign    |
  ⚛   | atomic-fetch     | this is the prefix:<⚛> operator
  ⚛+= | atomic-add-fetch |
  ⚛-= | atomic-sub-fetch |
  ⚛−= | atomic-sub-fetch | this operator uses U+2212 minus sign
  ++⚛ | atomic-inc-fetch |
  ⚛++ | atomic-fetch-inc |
  --⚛ | atomic-dec-fetch |
  ⚛-- | atomic-fetch-dec |