Fix the query planner so that it is able to use an index on a CAST expression.

FossilOrigin-Name: 2c886f3d49c9569e9f6ee28b89b57e2d4004c8972d11da0c23f7b2d2e0c9900a

diff --cc manifest
index ce24fd02dacaa5e8ce0e873b7219cba8245223a3,9e70bdab063f3ed89a44b2e714723f0fb289d1e5..638a3ec90b691c498d72b8f8f6130254938581a0
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Fix\sa\sbuffer\soverread\sin\sfts3\sthat\scould\soccur\swhen\saccessing\sa\scorrupt\sdatabase.
- D 2019-01-28T16:50:42.458
 -C Fix\sa\sperformance\sregression\scaused\sby\sthe\sprevious\scommit.
 -D 2019-01-28T18:58:54.614
++C Fix\sthe\squery\splanner\sso\sthat\sit\sis\sable\sto\suse\san\sindex\son\sa\sCAST\sexpression.
++D 2019-01-28T19:06:17.490
  F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
  F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
  F Makefile.in 9947eae873c07ae894d4c8633b76c0a0daca7b9fd54401096a77d1a6c7b74359
@@@ -1804,7 -1804,7 +1804,8 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P df04859a995571cd6faf1abe088725708f35e81195760274df9e2ec9bd47f69f
- R bde88f7bda44506e97f9208a864b23cb
- U dan
- Z 04d2112486f711cf461bcabac1e34620
 -P 3ef711d98fb239cf24472f124e7b36b0dde33355de5a2c9a3a978bbdd042a735
++P a9faf9033910927c74553e66c474d84ed3386f263cef3eec299e25d8306f410d c4db0ad12d4f3d2800d36404f391b325cdc4aa7f8dcea93b2d63a489d9095ad4
+ R 54fc32c05e999eaa7483855f7fbb2719
++T +closed c4db0ad12d4f3d2800d36404f391b325cdc4aa7f8dcea93b2d63a489d9095ad4
+ U drh
 -Z 51fba204c69fae1056723ec255ec3703
++Z d2bf11950d89b1b09c3cca064a694bb6

diff --cc manifest.uuid
index f3f266bcb12b5136351f2d936ebc9c682fbe63ef,b78f5c20ef3b7807eb3c5ee54d3ba1329d9f65fe..c96543994e3b618705a0440e9d9a26a5c998fb4f
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- a9faf9033910927c74553e66c474d84ed3386f263cef3eec299e25d8306f410d
 -c4db0ad12d4f3d2800d36404f391b325cdc4aa7f8dcea93b2d63a489d9095ad4
++2c886f3d49c9569e9f6ee28b89b57e2d4004c8972d11da0c23f7b2d2e0c9900a