Enhance the json_extract() function to reuse parses of the same JSON when

the function appears multiple times in the same query.

FossilOrigin-Name: 3ba9e7ab79e32090a71c7aa152da9bd5951940ae5e2cf433bceadeb6bfca193f

diff --cc manifest
index d5d926e20503a0c7bb0ef5bdacd7864848632229,9d3c8a80854155a640368a511622d04ccfe7bca5..5f2de8a3da489b251003b4008ac26bb838794482
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Do\snot\ssave\sthe\sstate\sof\san\sfts5\smerge\soperation\smid-way\sthrough\san\sinput\nterm,\seven\sif\sno\sprevious\sentry\sfor\sthat\sterm\shas\scaused\sany\soutput.\sDoing\sso\nmay\scorrupt\sthe\sFTS\sindex.
- D 2017-05-11T18:14:06.985
 -C Cache\sthe\sJSON\sparse\sused\sby\sjson_extract().
 -D 2017-05-11T16:49:59.245
++C Enhance\sthe\sjson_extract()\sfunction\sto\sreuse\sparses\sof\sthe\ssame\sJSON\swhen\nthe\sfunction\sappears\smultiple\stimes\sin\sthe\ssame\squery.
++D 2017-05-11T18:42:19.585
  F Makefile.in 1cc758ce3374a32425e4d130c2fe7b026b20de5b8843243de75f087c0a2661fb
  F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
  F Makefile.msc 6a8c838220f7c00820e1fc0ac1bccaaa8e5676067e1dbfa1bafa7a4ffecf8ae6
@@@ -1580,7 -1579,7 +1580,8 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P 3980ea0911b3ad3f86d7a7bdc6503f233315c274f473e18831e13eda2c238eeb
- R e8ce1902ba436a257e96b01caa3cadb9
- U dan
- Z c1b8197d958a390da1753ec3ab7dee72
 -P ff5306752e83e760255a10f20168c0f090929a4fee2a5f720dfab36f0ee72fae
 -R cae1848a63e8e13e207beadd6dc14b62
++P 9a2de4f05fabf7e725666fb8824ae1adad56834d7ae4f2e118375bb6f9c0ae77 44ca6c2c4639f3c50ae9233ee299ff0fc4566462c31f28d8676f8de7ffdcd7f0
++R 206babf55062a938db66e913be51f858
++T +closed 44ca6c2c4639f3c50ae9233ee299ff0fc4566462c31f28d8676f8de7ffdcd7f0
+ U drh
 -Z e9ec1c79d7987d6b2eda6f4466e2dc4b
++Z 601ecb610822b99db3531b28190b1d48

diff --cc manifest.uuid
index 8a1a73a65b1214a1aec21ab1321e6cd16b0cf708,a0274addc81eb8db2f961291e3a7e1f31e7e9f83..1ad89a97cc20353cd9171ce8b999959d1fd1fda7
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 9a2de4f05fabf7e725666fb8824ae1adad56834d7ae4f2e118375bb6f9c0ae77
 -44ca6c2c4639f3c50ae9233ee299ff0fc4566462c31f28d8676f8de7ffdcd7f0
++3ba9e7ab79e32090a71c7aa152da9bd5951940ae5e2cf433bceadeb6bfca193f