Add extra tests for database corruption inside the defragmentPage() routine,

as dbfuzz2 has found ways for corruption to leak into that point.  Add test
cases in fuzzdata7.db.

FossilOrigin-Name: 997b65117f8c12dba5fb85434fde9765cdb0d2a49cc3e31979abba3e21350086

diff --cc manifest
index d90f60545b598696a444015bdc895b0b9e6e5baf,bb664d696d55f37f3ab683a906c89b3eec735e6f..34ddbff50bfc6b4c8188d300aaeab2bb7d0b3796
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,10 -1,10 +1,10 @@@
- C Fix\sa\sproblem\sin\ssqlite3BtreeDelete()\sin\swhich\sdeleting\san\sentry\sfrom\sa\ncorrupt\sdatabase\scan\sleave\sa\sbtree\spage\swith\szero\scells.
- D 2018-12-13T21:05:45.342
 -C Merge\sthe\sdbtotxt\senhancement\sfrom\strunk.
 -D 2018-12-13T15:52:31.619
++C Add\sextra\stests\sfor\sdatabase\scorruption\sinside\sthe\sdefragmentPage()\sroutine,\nas\sdbfuzz2\shas\sfound\sways\sfor\scorruption\sto\sleak\sinto\sthat\spoint.\s\sAdd\stest\ncases\sin\sfuzzdata7.db.
++D 2018-12-13T21:11:22.437
  F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
  F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 -F Makefile.in 2f1b61ac62689ca4e9cbff9fdb359578ea37ddd9252355ec0b7b9700ad56fe90
 +F Makefile.in d8b254f8bb81bab43c340d70d17dc3babab40fcc8a348c8255881f780a45fee6
  F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 -F Makefile.msc 2ef13d6845b899eaaa6122c69b74175656a97e26666567af795f4cfe41b7a673
 +F Makefile.msc 3c4c7e94419ff28cb68850188c9d153b343aed4c5ebed5965426232ed67ff9d9
  F README.md 377233394b905d3b2e2b33741289e093bc93f2e7adbe00923b2c5958c9a9edee
  F VERSION 453e2f4529ca208196d5567db28d549d7151f79efd33f6e6cfe6e613e583a0be
  F aclocal.m4 a5c22d164aff7ed549d53a90fa56d56955281f50
@@@ -448,7 -448,7 +448,7 @@@ F src/auth.c 0fac71038875693a937e506bce
  F src/backup.c 78d3cecfbe28230a3a9a1793e2ead609f469be43e8f486ca996006be551857ab
  F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
  F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
- F src/btree.c d4bf14ab64339017db65a17c70a3b3d5edf39e5ec5373921133407a56c3e50e5
 -F src/btree.c 3d898feaeff97c934cb6ae557265e43ba1f473de6a9e64e947a364bdb6c4f563
++F src/btree.c e3e08171f90c6843d2a26d582d946a754093435acd48155b8cd339b06cc8cc1b
  F src/btree.h febb2e817be499570b7a2e32a9bbb4b607a9234f6b84bb9ae84916d4806e96f2
  F src/btreeInt.h 620ab4c7235f43572cf3ac2ac8723cbdf68073be4d29da24897c7b77dda5fd96
  F src/build.c ef9d7dc73e40dd9d10c28848343e21e8bc1baaab92cfb75eda893fff4fbf6b55
@@@ -1787,7 -1786,7 +1787,8 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P 1f583c53f3b7318c69f6e235934d97ef9493278feeab0837217076d7d071c35b
- R bdea9a4eb87ba8aa256dc24af3d20da1
 -P b4210d320c6426d2838d4cc08709fdfd015c1c95fcad9a5f9e8fd390c23b9fad e3bf1d3ea5f748c5142c2403813fdace5aedc1fc68f0dcd5eae40a2fe763fedb
 -R f29a990b635857a4ac73167c7e81e845
++P 682053d1e603c21b8085c39db618a39b23ec8d2c4d822fd19634db0e03038ea2 b386fce9a23e628dce7362dcca2904b8d0af6da58a6fe6eb7f12f058a8363e49
++R a1122995324223304196c0f63a35c59e
++T +closed b386fce9a23e628dce7362dcca2904b8d0af6da58a6fe6eb7f12f058a8363e49
  U drh
- Z 2389e6a9c76519655c1cfe39d2b8ef15
 -Z 899a9ea598b74391d5cfbd03300f9f81
++Z b4a67e64bc03ae62ccd56c8eb96ba51d

diff --cc manifest.uuid
index d63fa51aed59a4c627e79729f2cb8e5bac535104,1f8aa015e208456d9b0cad027eef2e550b482756..f411d662da0d381cdfcc702a8d1fa5006b918b54
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 682053d1e603c21b8085c39db618a39b23ec8d2c4d822fd19634db0e03038ea2
 -b386fce9a23e628dce7362dcca2904b8d0af6da58a6fe6eb7f12f058a8363e49
++997b65117f8c12dba5fb85434fde9765cdb0d2a49cc3e31979abba3e21350086

diff --cc src/btree.c
Simple merge