If a client submits data that is not NFC-normalized Unicode or that
contains C0 controls other than HT, LF, and CR, it gets normalized before
the API ever sees it. Which can lead to difficult-to-handle bugs when,
for example, a title is subject to normalization so the client can't
find the specific title it submitted anywhere in the response (T139130).
This patch does two things:
* Detects when normalization was applied to an input value (at the
MediaWiki level, anyway; if PHP or earlier does it we're just out of
luck) and add a warning to that effect.
* For ApiPageSet's 'titles' parameter, split into the individual titles
and add them to the 'normalized' list in the response. This requires
encoding the pre-normalized strings to avoid ApiResult's own
normalization.
Bug: T29849
Bug: T144071
Change-Id: I215fd3edd7a5e1b45292e60768bf6dd5ad7f34de
087e25021b