Changes to avoid loading large records into memory within VACUUM.

FossilOrigin-Name: 56a54258560fab715b83967634b2bd4c04be43cded112b46e85da9f99ee02f7c

diff --cc manifest
index ead9a8fa607d709580c585175630e2cddb0cc2ef,44b269d0ac6dfb5a501b0dbba27d5feb4ee9562a..2b7531deb8e781761c84fc76c0ea03f9fa1371b8
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Add\san\soptional\sfunction\sto\sthe\schsumvfs\sextension.\s\sWhen\sactivated\sby\nthe\sSQLITE_CKSUMVFS_INIT_FUNCNAME\smacro,\sthis\sfunction\swill\sinvoke\sthe\nfile-control\sthat\ssets\sthe\snumber\sof\sreserved\sbytes\sto\s8.\s\sThis\scan\sbe\nused\sto\sinitialize\sa\scksumvfs\sdatabase\sfile\sby\sprogramming\slanguages\nthat\sdo\snot\shave\saccess\sto\sthe\ssqlite3_file_control()\sinterface.
- D 2020-12-10T13:49:00.833
 -C Fix\sminor\sissues\swith\snew\scode\son\sthis\sbranch.
 -D 2020-12-10T19:20:15.980
++C Changes\sto\savoid\sloading\slarge\srecords\sinto\smemory\swithin\sVACUUM.
++D 2020-12-10T19:51:39.987
  F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
  F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
  F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@@ -1888,7 -1889,7 +1889,8 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P c0de6c1fb2c486be1da01e5e4ca8c5634ba37822e418d57f272e018c3e3fc0a2
- R 6c67d7c383f4b37d548756594c8d9b75
- U drh
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 -P 7337eed629b4537b8fc2dc87c3c71d0a664128a91fd00f3c5f18843505beee90
++P 01841fb4bf3d6c5fd5bcbc7d1338998c50f69f84ca475fba7cf764d636714678 f7fa76d0963e7b34026dc20c920bfbf7961033fe2b99503f6857157595f86823
+ R 4dec8f74318b8721d36ac1bd02f7a778
++T +closed f7fa76d0963e7b34026dc20c920bfbf7961033fe2b99503f6857157595f86823
+ U dan
 -Z 1308f2122d2b4d2b55d5a48e115dbda3
++Z 3adf74c0105eb40ca1b5c5d7fdb48232

diff --cc manifest.uuid
index 782a536fd6c93c401bb0809419c9936f9a3d6cca,7aba6f714d52c7016047ebd010a49b27690b018a..c98df885d4ab7d3a8dcdfb36e554c7c65ce7ede9
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 01841fb4bf3d6c5fd5bcbc7d1338998c50f69f84ca475fba7cf764d636714678
 -f7fa76d0963e7b34026dc20c920bfbf7961033fe2b99503f6857157595f86823
++56a54258560fab715b83967634b2bd4c04be43cded112b46e85da9f99ee02f7c