Add the SQLITE_FCNTL_CKPT_START file-control and use it to optimize

the cksumvfs extension.

FossilOrigin-Name: efdecb13091316aeac2722f58577cb0314e008e857f2816a2a222bac0a83e9e1

diff --cc manifest
index 5e7d1c29a4cb7baa07addc29439e54acde76b70d,ef2565abcc439c3b58b25f2e91d2dfa165840ce8..cda7604ccfd043be373aa32c6ac5a16087bb4a8e
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Add\ssupport\sfor\sPRAGMA\sanalyze_limit\sand\sapproximate\sanalysis.
- D 2020-05-02T03:46:32.798
 -C Add\sthe\sSQLITE_FCNTL_CKPT_START\sfile-control.\s\sUse\sit\sto\soptimize\sthe\ncksumvfs\sextension.
 -D 2020-05-01T18:37:34.019
++C Add\sthe\sSQLITE_FCNTL_CKPT_START\sfile-control\sand\suse\sit\sto\soptimize\nthe\scksumvfs\sextension.
++D 2020-05-02T04:08:23.053
  F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
  F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
  F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@@ -533,12 -533,12 +533,12 @@@ F src/printf.c 9be6945837c839ba57837b4b
  F src/random.c 80f5d666f23feb3e6665a6ce04c7197212a88384
  F src/resolve.c d36a2b1639e1c33d7b508abfd3452a63e7fd81737f6f3940bfef085fca6f21f4
  F src/rowset.c ba9515a922af32abe1f7d39406b9d35730ed65efab9443dc5702693b60854c92
 -F src/select.c c310de94bf67315054587c18a16e7a3e3dc3a98dc79168f0c2b776548d43f6cd
 -F src/shell.c.in 86cd0f0412b9739b769fafdfcad28f731882d522042a95c30ab033a5eba68b03
 +F src/select.c 1720bff2168491ca79af81a03bd18c0383f61d845c6e17caff9d25aabc4ab435
 +F src/shell.c.in cf2d24f54412c06e5fb34af7fabc748651125e1dceac29b740e91f06d23447b6
- F src/sqlite.h.in b20d5dc52765ff82f3701395a7e670611ddf138ee0ae84482452ad3a0b5f24b5
+ F src/sqlite.h.in 00fdd0a9cdcb4ca3ea6aed8466a23e158c4a2feb5c2552de62c70f40d2418289
  F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
  F src/sqlite3ext.h 2d1af80082edffd71c6f96f70ad1ce6a4fb46615ad10291fc77fe0dea9ff0197
 -F src/sqliteInt.h 0f3848c46310d197246003f052985b72d1cdbfc0b31e069db76cb5231062fa1d
 +F src/sqliteInt.h 1f6909cd268d1cda2f04914d150997b17afd8ff7e5cf1930cc1f88d337a49f74
  F src/sqliteLimit.h 95cb8479ca459496d9c1c6a9f76b38aee12203a56ce1092fe13e50ae2454c032
  F src/status.c 9ff2210207c6c3b4d9631a8241a7d45ab1b26a0e9c84cb07a9b5ce2de9a3b278
  F src/table.c b46ad567748f24a326d9de40e5b9659f96ffff34
@@@ -614,10 -614,9 +614,10 @@@ F src/vdbeblob.c 253ed82894924c362a7fa3
  F src/vdbemem.c 39b942ecca179f4f30a32b54579a85d74ccaefa5af2a0ad2700abe5ef0768b22
  F src/vdbesort.c 2be76d26998ce2b3324cdcc9f6443728e54b6c7677c553ad909c7d7cfab587df
  F src/vdbetrace.c fa3bf238002f0bbbdfb66cc8afb0cea284ff9f148d6439bc1f6f2b4c3b7143f0
 +F src/vdbevtab.c 8094dfc28dad82d60a1c832020a1b201a5381dc185c14638affc6d4e9d54c653
  F src/vtab.c 7b704a90515a239c6cdba6a66b1bb3a385e62326cceb5ecb05ec7a091d6b8515
  F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
- F src/wal.c ea8dad28bb0e2b85ac1ab7618968687ff5fd522af8a1a38d6960ec176ebc8ee6
+ F src/wal.c 8efa749ff1e84fb69127bdab1d0f3545afc1706f4dde6f19f2f6237d7dc9c2d2
  F src/wal.h 606292549f5a7be50b6227bd685fa76e3a4affad71bb8ac5ce4cb5c79f6a176a
  F src/walker.c 7c429c694abd12413a5c17aec9f47cfe9eba6807e6b0a32df883e8e3a14835ed
  F src/where.c 9546c82056e8cdb27291f98cf1adca5d271240b399bb97b32f77fc2bea6146c9
@@@ -1863,8 -1862,10 +1863,8 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P d09bcce37f1eaf084e3b07eb4a23653ea1f370cdd290ce3875408186adf87022 77a55c394d2c313a5710229bee9262457dcfc6620e6500f9f526c5f6acf87cef
- R 4ed29fc45141d3045a102a3aecbc1dee
- T +closed 77a55c394d2c313a5710229bee9262457dcfc6620e6500f9f526c5f6acf87cef
 -P 853703cd6d44d6dd48ef5eda6523e374b8ebdf7c338ddaad31c15a40a8b3fd9b
 -R d02abd9a5af9bd115679571d54eadf06
 -T *branch * ckpt-start-fcntl
 -T *sym-ckpt-start-fcntl *
 -T -sym-trunk *
++P 812547525d35df975f40cbbeb604cc9cd2dec809c1ca083cbb139fe59ffa1d73 b40f5aa344ae10cf4da83b3aa9e4866d6f6ffb06ba7e34ec1ce80c92468cf3bf
++R 3e884a6ea8a79fc4f9e8f6323bb6c8f0
++T +closed b40f5aa344ae10cf4da83b3aa9e4866d6f6ffb06ba7e34ec1ce80c92468cf3bf
  U drh
- Z 44d724364acf9e8bd25af4207bb5887c
 -Z 843d07fcbc8456358389e1c6f788c09d
++Z aad739fd1c906055ab76678a6dc49335

diff --cc manifest.uuid
index 50f4b2e862106392cda35dff363e540204f46222,ce1bb2e80e2b83388e5fc6e986a408acdf85c122..54697a170e23664afe55399dbffaf6c3fea7c89e
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 812547525d35df975f40cbbeb604cc9cd2dec809c1ca083cbb139fe59ffa1d73
 -b40f5aa344ae10cf4da83b3aa9e4866d6f6ffb06ba7e34ec1ce80c92468cf3bf
++efdecb13091316aeac2722f58577cb0314e008e857f2816a2a222bac0a83e9e1