Add requirements marks and make minor tweaks to documentation.
When enlarging the size of a StrAccum object, use sqlite3DbMallocSize() to
record the entire size of the allocation, not just the requested size.
Use exponential buffer size growth in StrAccum, as long as the size does not
grow to large, to avoid excess memory allocation resize operations.  Also,
document the fact that setting scratch memory causes SQLite to try to avoid
large memory allocations.
Add the experimental sqlite3_stmt_scanstatus() API. For comparing the number of rows actually visited by a loop with the estimate used by the query planner.
Updates to the sqlite3_stmt_scanstatus() documentation.  No changes to code.
Add the SQLITE_CONFIG_PCACHE_HDRSZ option for sqlite3_config().
Improved documentation and addition of source-code evidence marks for the
sqlite3_config() interface.
Change the definition of SQLITE_CONFIG_SCRATCH so that at most one scratch
buffer is used per thread.  Use the generic heap memory allocator for the
WalIterator object when running a checkpoint.
Add various requirements evidence marks for sqlite3_config() options.
For the Win32 VFS, allow memory mapped files to work when compiled without WAL support.
Skip tests that require WAL mode when it is not enabled.
Improved output formatting for the showstat4 tool.
Add the ".scanstats on" command to the shell tool. Executing this command causes the shell tool to print values from sqlite3_stmt_scanstatus() after each query is run.
Enhance whereLoopCheaperProperSubset(X,Y) so that it does not report true
if X uses skip-scan less than Y, since in that case X might
deserve to be cheaper even if it is a proper subset.
Add a test case to check that the previous commit is effective.
Make sure that NULL results from OP_Column are fully and completely NULL
and do not have the MEM_Ephem bit set.  Fix for ticket [094d39a4c95ee4].
Change the query planner to do a better job of estimating the number rows
selected by a BETWEEN operator using STAT4 when both upper and lower bounds
are contained within the same sample.
Fix harmless compiler warnings in the new balance_nonroot() routine.
Fixes to the Windows VFS to allow memory mapped files to work without WAL support.
Change the SQLITE_SCANSTAT_EST parameter so that it returns a double for
the estimated number of output rows per loop, rather than a 64-bit integer.
Revise the output format for the ".scanstats on" in the shell to make use
of this new capability.