Make sure "rowid" columns are correctly resolved in joins between normal
tables and WITHOUT ROWID tables.  Fix for ticket [c34d0557f740c45070].
Remove the "rowid cache" that sought to remember the largest rowid for a
table and thereby speed up OP_NewRowid.  That cache was ineffective.
Removing it results in a performance increase of 0.4%, less memory usage,
and a slightly smaller library size.
Minor simplifications to the "zeroPage()" routine in btree.c.