Merge appendvfs updates and testing.

FossilOrigin-Name: 63fcf301fedf1f3708e2226ed499a53b3e9c1d2cc2b17d4b0b736e36aff0ae74

diff --cc manifest
index 20d179021a632306b26de9c48a1776b84c75d3b2,3df837eca00b9962434e38d21846150fbe5a6485..c40f25dac06aca8c74375e2e8fc9be84d22feace
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Limit\sparenthesis\snesting\sdepth\sin\sFTS3\sexpressions\sto\nSQLITE_MAX_EXPR_DEPTH.
- D 2021-03-06T15:13:26.136
 -C Require\sthat\sthe\sappendvfs\ssuffix\smark\sindicate\sthat\sthe\sappended\sdatabase\nbegins\sat\san\soffset\sthat\sis\sa\smuliple\sof\s512\sand\sthat\sthe\sappended\sdatabase\ncontains\sat\sleast\s512\sbytes.
 -D 2021-03-08T13:45:08.970
++C Merge\sappendvfs\supdates\sand\stesting.
++D 2021-03-08T14:26:22.390
  F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
  F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
  F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@@ -1909,7 -1910,7 +1909,7 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P 01eae68e85b31b7a9f08733459765bbd9bf9dad592bf64f10fc2fa32e02a89c2
- R 02b7be7b0db655498be572d780795257
 -P 92989fc56f2e81ac13f8106ec83c930f43d10715269b988ee47c9bfa53621995
 -R 95e6ca76a30ea77bdd3f5fbf1f80121b
--U drh
- Z 8b3ef9b5e97e19a6fa18878f5257830d
 -Z b77a3ba4a0e4bc82984a421652c390d8
++P 5ddd8032ef9ecd5b53909d304c8f1375a72f270fd7810964cb4e385e25bedd4f aeb87cc70495dd172e170eff31fd754331d4b979c0b649ab239f8c5c0c76e695
++R 8ccab392163487da9b54671965ff97af
++U larrybr
++Z 884cfbe97fea0184c4337b606da309e4

diff --cc manifest.uuid
index e9ca6e77849fdfd21a0215224967b0d771bdfba6,83924179eebf3e17b54d8649a1e8fea45e83210f..91a73abd3d9e5490409280f3b84c3a8c4c77ee06
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 5ddd8032ef9ecd5b53909d304c8f1375a72f270fd7810964cb4e385e25bedd4f
 -aeb87cc70495dd172e170eff31fd754331d4b979c0b649ab239f8c5c0c76e695
++63fcf301fedf1f3708e2226ed499a53b3e9c1d2cc2b17d4b0b736e36aff0ae74