Optimization: Try to avoid unnecessary btree searching when repositioning

a cursor to the next row.

FossilOrigin-Name: ee793d30c1dc1f78f49e6230d17750eceedbd8ed

diff --cc manifest
index 09b8ee5078540d66bf08e32c8d928d7b39551b66,95352ee96a32b9db870816919d7edc8dcdaa3556..3e45f5ecce940706008885dcf644523c9df628ea
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Add\sthe\smissing\sSQLITE_API\ssymbol\sto\stest_delete.c\s(it\sis\snot\sadded\nautomatically\sas\sthis\sfile\sis\snot\spart\sof\sthe\samalgamation).
- D 2017-01-23T15:58:09.428
 -C A\sbetter\simplementation\sof\sthe\smoveto-neighbor\soptimization\sthat\schecks\sfor\nnearby\srows\son\sadjacent\spages.
 -D 2017-01-21T21:47:54.621
++C Optimization:\sTry\sto\savoid\sunnecessary\sbtree\ssearching\swhen\srepositioning\s\na\scursor\sto\sthe\snext\srow.
++D 2017-01-23T16:56:18.240
  F Makefile.in 41bd4cad981487345c4a84081074bcdb876e4b2e
  F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
  F Makefile.msc b8ca53350ae545e3562403d5da2a69cec79308da
@@@ -1547,7 -1547,7 +1547,8 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P 03c601344ed56b316bcc5fd02f6648b0009ba61b
- R 9417217ad349116acb540369984c5408
- U dan
- Z b2f31778ddace8b8427e4711f64f3edb
 -P 8e5cfb2039126da7689c4b1c88760f10e1234eaf
 -R 9f1865839aca85688e5829c506350f09
++P 7a4f512ddf9e7e718389c80930d6268ab598459c 2c4ecb85a475b9063aa8a3bb517ac181a7ded649
++R 29a4885c53e914cde79778fd2e323ab3
++T +closed 2c4ecb85a475b9063aa8a3bb517ac181a7ded649
+ U drh
 -Z fbf63ba541a6f5ec3e59c684016e63a0
++Z 5710c3bf174cb3e3f9b43957024c6c5f

diff --cc manifest.uuid
index e9d2ae6e41bea9d45429d2b4a4548b473504a8ad,478c310b2772944995474edd780e847378ba92b9..2e7c43d7572f70ce661be296ae6670ef1fb010b1
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 7a4f512ddf9e7e718389c80930d6268ab598459c
 -2c4ecb85a475b9063aa8a3bb517ac181a7ded649
++ee793d30c1dc1f78f49e6230d17750eceedbd8ed