Use macro wrapper to access PGPROC data, to improve compatibility with PostgreSQL forks.

Remove compliation warning of unitialized value

Search for SLRU page only in its own bankOne of the two slot scans in SlruSelectLRUPage was not walking only the slots in the specific bank where the buffer could be; change it to do that.

Moved the use of the cronJob a further down, since it may not be relevant if the task is cancelled.

Improve performance and reduce table sizes for case mapping. The main case mapping table stores only 16-bit offsets, which can be used to look up the mapped code point in any of the case tables (fold, lower, upper, or title case). Simple case pairs point to the same offsets.