In the vfslog extension for FILECONTROL records, show the pragma name for
SQLITE_FCNTL_PRAGMAs and the requested size for SQLITE_FCNTL_SIZE_HINT.
Further enhance the vfslog extension to record the number of freelist pages
and the first freelist page in CHNGCTR-READ and CHNGCTR-WRITE records.
Add the SQLITE_FCNTL_TRACE file control and generate it for OP_Trace
when compiled with SQLITE_USE_FCNTL_TRACE.  Update vfslog.c to make
use of the new file control.  Also update vfslog.c to log UNLOCK events
before the fact, rather than afterwards.