Fix recent breakage of the appendvfs extension.

FossilOrigin-Name: 7dbbe5b34eea31ea54a5804035d4d0dfeb09c42cd9ab337e1e64c1296decbef3

diff --cc manifest
index 3349d89c12b1011212813f18133e8c6208be4687,57975f75a1507959e12cf436b4c8f520b4b81c36..a34ce6b9ec88f783f71f95efa4132c7b18e7e79a
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Fix\sa\sproblem\swith\sALTER\sTABLE\sRENAME\sCOLUMN\swhen\sused\son\sa\sschema\sthat\sfeatures\sgenerated\scolumns.
- D 2021-03-16T11:11:07.514
 -C Comment\sand\sstylistic\schanges\sto\sthe\sappendvfs.c\simplementation.
 -D 2021-03-16T14:12:26.803
++C Fix\srecent\sbreakage\sof\sthe\sappendvfs\sextension.
++D 2021-03-16T14:26:56.216
  F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
  F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
  F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@@ -1910,7 -1910,7 +1910,7 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P aea12399bf1fdc76af43499d4624c3afa17c3e6c2459b71c195804bb98def66a
- R 8d9ba034916265e30952367e14ccf2d0
- U dan
- Z 66abaaaa0bcfb13bbe669b759bf47eeb
 -P 3aedf818c1cfc88ee1103abd8b20e787f6be1bcc4c9350963f0cd52f5ac04154
 -R d4d0d407c45719772ccdc3772a06a769
++P 0e255b26872b50581d470952dd98e21dd82d081885006f58d49daa4b4576b35d 25c3186aa143328157fb506a29802e87099cd14be4fa218230484a3212f20621
++R 7058d428dd88d4e4a708c5dd000f40bd
+ U drh
 -Z 2e9ac8f611b5ac99207230cf538d46c9
++Z 11c2dd0109baa6fbadbea6ed933cddce

diff --cc manifest.uuid
index bed7091db56cd908021496153528863ea347a09e,283bb8a43534bc1f80a46a1def774a5e7a61e75a..99057c7d8fe6dddff1227bf37b6bac34cbaf85b5
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 0e255b26872b50581d470952dd98e21dd82d081885006f58d49daa4b4576b35d
 -25c3186aa143328157fb506a29802e87099cd14be4fa218230484a3212f20621
++7dbbe5b34eea31ea54a5804035d4d0dfeb09c42cd9ab337e1e64c1296decbef3