Start a new branch for release 3.6.22 plus limited enhancements and fixes.
This first check-in includes the performance enhancements of check-ins
[26cb1df735], [61a2c8d4d6], and [27dc5b1c52]
Merge in the fix for VACUUM on auto_vacuumed databases with large schemas.
Check-in [86d50ce57f].  Ticket [da1151f97df].
Enhance integrity_check to detect out-of-order rowids.  This is a
cherrypick merge of check-in [cae47c5b09].
Fix a segfault that is possible for an OOM fault in ATTACH when in
shared-cache mode.  This is a cherrypick merge of check-in [e37137376a].
Merge in all of the logging enhancements.  This is a cherrypick merge of
the following check-ins: [103321e37a], [a8076aede3], [6d910245ad], 
[7c4cca6d1a], [edea3bb740], [1a6d4bb130], [a8c984c1d6], [69a493182f], and
[1168763d2c].
Expire pragma statements when reset, even if they were not run to completion.
When TEMP files are in memory, also put the massive TEMP file used by
the VACUUM command in memory.  This is a cherry-pick merge of
[9daf4e7d07]
Modify the sqlite3_log() interface and implementation so that it never uses
dynamic memory allocation - to avoid deadlocking when called while holding 
the memory allocator mutex.  Cherry-pick merge of [28d1bc98d6].
Sync the database file after a rollback.  This is a cherrypick merge
of check-in [b21b911f23].