* Make a cache key with database-agnostic prefix.
*
* Doesn't have a wiki-specific namespace. Uses a generic 'global' prefix
* instead. Must have a prefix as otherwise keys that use a database name
* in the first segment will clash with wfMemcKey/wfForeignMemcKey.
*
* Make a cache key with database-agnostic prefix.
*
* Doesn't have a wiki-specific namespace. Uses a generic 'global' prefix
* instead. Must have a prefix as otherwise keys that use a database name
* in the first segment will clash with wfMemcKey/wfForeignMemcKey.
*