Changes to allow some multi-row UPDATE statements to avoid the two-pass

approach.

FossilOrigin-Name: 7ae6104a3e0d1d2cacfe2be732f0220a53908132

diff --cc manifest
index 60b608e6c70f956ae72439113e42b35cffa831b9,dc4ff7c1a4186c1209bf9ae87b21aca14da3ba45..62ade5afe1873354c86f978f971f2eefc62b2da5
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C In\sthe\sSTAT4\scomputations,\sensure\sthat\sthe\saAvgEq\svalues\sdo\snot\sgo\snegative.
- D 2017-01-11T14:15:29.635
 -C Fix\sa\sproblem\scausing\sthe\spre-update\shook\sto\sbe\spassed\san\sincorrect\srowid\nvalue\sin\ssome\ssingle-pass\smulti-row\supdates.
 -D 2017-01-11T20:10:30.712
++C Changes\sto\sallow\ssome\smulti-row\sUPDATE\sstatements\sto\savoid\sthe\stwo-pass\napproach.
++D 2017-01-11T21:03:53.460
  F Makefile.in 41bd4cad981487345c4a84081074bcdb876e4b2e
  F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
  F Makefile.msc b8ca53350ae545e3562403d5da2a69cec79308da
@@@ -1543,7 -1544,7 +1544,8 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P e500c15a9f55aed1601f7c14169dd56fd76f1fdd
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++P f58f75b5a06f88ba97bd1a02bee621c64691c6f8 62257eb53c13d4c7ed128d5d89f6f10d4aff945c
++R a5d3781c66cde36056f7269332c03001
++T +closed 62257eb53c13d4c7ed128d5d89f6f10d4aff945c
+ U dan
 -Z 064d431f5a23ac6118a97592b16afa49
++Z 8a4ce767e7a0e27eb39847a70d667c24

diff --cc manifest.uuid
index 1657a590c98c840e1cce7a669cdec11bd758efa6,19077faa6c5d02e6870203c15258eae59f55822f..5a73a263e8619e02956ba5c3f919afda7f4d6611
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- f58f75b5a06f88ba97bd1a02bee621c64691c6f8
 -62257eb53c13d4c7ed128d5d89f6f10d4aff945c
++7ae6104a3e0d1d2cacfe2be732f0220a53908132