* Fix a long-standing bug where non-ASCII characters in search terms,
  including accented letters, would not match characters in a different
  case.
* Fix a long-standing bug where search terms using combining accents
  would not match display names using precomposed accents and vice
  versa.

To fully take effect, the user directory must be rebuilt after this
change.

Fixes #14630.

Signed-off-by: Sean Quah <seanq@matrix.org>