For rationale, see https://github.com/php/php-src/pull/6787
Make extension checks lowercase, add a special case for opcache
that has internal name not matching .so filename.
Extensions migrated in part 2:
* dom
* exif
* fileinfo
* ffi
DOMCharacterData::appendData() with no arguments.
DOMCharacterData::deleteData() with count exceeding string size.
DOMCharacterData::deleteData() with no arguments.
DOMCharacterData::deleteData() with offset exceeding string size.
DOMCharacterData::insertData() with no arguments.
DOMCharacterData::replaceData() with no arguments.
DOMComment::__construct() with more arguments than acceptable.
DOMDocumentFragment::__construct().
DOMDocumentFragment::__construct() with too many errors.
DOMDocumentFragment::appendXML() with no arguments.
DOMDocumentFragment::appendXML() with children with properties.