Add UPDATE FROM compatible with postgresql.

FossilOrigin-Name: 88baf1eb0706503214012520be4d872594ccc5b4c9674c44cc07b67ade2bfcf2

diff --cc manifest
index 22fbaef2024281e20f1442fbbbd163700465f3a7,502d27013f1512e44f7fc20d2546a003fbc595e0..a47c9a7eedc2daf6b675cf04ab23ed372a171746
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,6 -1,6 +1,6 @@@
  B 7a876209a678a34c198b54ceef9e3c041f128a14dc73357f6a57cadadaa6cf7b
- C Relax\spointless\srestrictions\son\sallowing\stables\sin\sthe\sFROM\sclause\sfrom\ncrossing\sover\sLEFT\sJOINs,\sas\slong\sas\sthe\stable\sbeing\smoved\sis\snot\sthe\nright\stable\sof\sthe\sLEFT\sJOIN.
- D 2020-07-16T18:55:58.182
 -C Add\sALWAYS()\saround\sa\sconditional\sthat\sis\salways\strue.
 -D 2020-07-17T22:20:23.013
++C Add\sUPDATE\sFROM\scompatible\swith\spostgresql.
++D 2020-07-18T15:52:15.996
  F Makefile.in 19374a5db06c3199ec1bab71ab74a103d8abf21053c05e9389255dc58083f806
  F Makefile.msc 48f5a3fc32672c09ad73795749f6253e406a31526935fbbffd8f021108d54574
  F autoconf/Makefile.am a8d1d24affe52ebf8d7ddcf91aa973fa0316618ab95bb68c87cabf8faf527dc8
@@@ -15,26 -15,32 +15,33 @@@ F ext/lsm1/lsm_unix.c 11e0a5c19d754a4e1
  F ext/misc/decimal.c c1897f624893d1c12e3c879d97ca7d1c4a36cae10d32afe632779de78c4aaa4f
  F ext/misc/ieee754.c bb6bd8e9eeeda5a7ac82839fcab5c0b8156b0532165387cc5458a97f60047b5d
  F main.mk b1cd0bc6aedad7ebb667b7f74f835f932f60ee33be2a5c3051fd93eb465f5c75
+ F src/alter.c c63fb72ae0ca39175996fcf7008d44022a7ea99e03c0af3e1d968505ceff7120
+ F src/attach.c 0b11e00c166b622c84ec176773b1d691c61ad07d247809e3e1635d4e99e71d30
  F src/btree.c b8b0e80c8bbe4e1fb35ae559e9e9aa009799c20cf12f159ebb503b05be1fab9b
  F src/btreeInt.h 19267385aa3bc00067d48e0e4ba83ae82dc08b0c15a3b3df20ea653cb462b5bf
- F src/build.c ba1bbe563a3dc02d5fed20537603181e5289c13ea30ae5e775f552e7557adbfa
+ F src/build.c 45d912640987426442eb9eeec695c4dd45dd440b4cd27e8c13a42eed2fa87dcd
+ F src/delete.c 410c771c25afc113c273d9efad6ab6881bda28c75a1838b9d2c52ba20d1dc704
  F src/expr.c 90039a043658ce78c3237ba5064c0934b7294120f6adc387f8d0fba306028154
- F src/parse.y b6b4b02f8cc8f94ac1d93a922543e0344dbb30b04877898736c01ec7ec03eaaa
 +F src/malloc.c 22d5bdd9fe88ae4fad1b91a1b9735104b82853ffef868f1f05517d60dc1875f5
+ F src/mem2.c b93b8762ab999a29ae7751532dadf0a1ac78040308a5fb1d17fcc365171d67eb
+ F src/parse.y ecb9abdd79ec86c8dca7cb126bbdcf322c0e282f87a6d0d734ea5f2c57ced516
  F src/pragma.c ae499b5ab8f4e833f67e28bf2322500e9aa612aadf12581d1324333f848d8b51
  F src/pragma.h 8dc78ab7e9ec6ce3ded8332810a2066f1ef6267e2e03cd7356ee00276125c6cf
- F src/resolve.c 79cee37182fea66703f90365b8b0a646ed7e9bfa9238b91fa90dfc74258b940e
- F src/select.c 5293c60dd32c87a599b16e6f4acaf2827b7f60fca317b614a7cfccfb0beecba9
+ F src/resolve.c 2dd6821aac2cd27de9fcf6aa6d1f8c41b4b5841c9bc58bf1c9109008009a3a2e
+ F src/select.c ee84981a346ddddf5669db441a68fac763f4266fe83a9cb27e43c67fbcf1b215
  F src/shell.c.in 81fa23ac1a3d6ac9ed13e9ae711a3d8806396ca7cc12c5d6a2e2536f70b0c7ad
- F src/sqliteInt.h 8366e482a1330e9c103c9c9053c53894e373daf1fb9dd65bd953ffc0b3ad7a8b
+ F src/sqliteInt.h 9682c3ce6b970b3a997d65c140bdb5b286a04188e4e1c8489b64a525161ecb30
  F src/test1.c fe56c4bcaa2685ca9aa25d817a0ee9345e189aff4a5a71a3d8ba946c7776feb8
- F src/update.c 6a0484134635f167594d597a33d186051125d3ef41803a90b246cea6cf7f11f9
+ F src/test_malloc.c 21121ea85b49ec0bdb69995847cef9036ef9beca3ce63bbb776e4ea2ecc44b97
+ F src/trigger.c ef67bde309a831515dc3c2173d792574309f2f42d45f8c078743fae9f7f98c75
+ F src/update.c e917882ce2a8529ab361500b62ff6d3f0839b946f696d2ec3b048774ff11e37f
  F src/util.c c0bacc165f46169d2b720c37c8719165e383211698fad1de39dd16a8c161815a
  F src/vdbe.c 981666c49d33039df6dc9fccd40191575586ac4866255b2f57819cc5eb99f572
  F src/vdbeapi.c c1a9004ac554d8d48794d2ce5f80397f8e419fd28643a543cc1e004c7713c3ef
 -F src/where.c 35cb38d45294118e484fd3a8011aaee8ebe96b28855a6913575a7fe3722d7af5
 +F src/where.c 2ea911238674e9baaeddf105dddabed92692a01996073c4d4983f9a7efe481f9
  F src/window.c 0dec178bfa541c757d15a2be78f34aea36393a0966600366810e5f8739ccf370
  F test/altertab.test b8b2104212e8ea87c75c3cbe3cb78ed7236a6c828ee2e59ed09d3dbe9812d002
+ F test/altertab3.test d0d51e652aaa11e37de1f1215181d88334fefcb185f3b9bd91e06e98260c4694
  F test/busy2.test 415364312743992641f9bf679c84918327296067f85a5d00012b339dc35acbd7
  F test/corruptL.test 01cfda6b28f463d1713ac72a101e65549250568129ce5317ec6729729ecaf477
  F test/decimal.test fcf403fd5585f47342234e153c4a4338cd737b8e0884ac66fc484df47dbcf1a7
@@@ -53,7 -68,7 +69,8 @@@ F tool/mksqlite3c.tcl f4ef476510eca4124
  F tool/mksqlite3h.tcl 1f5e4a1dbbbc43c83cc6e74fe32c6c620502240b66c7c0f33a51378e78fc4edf
  F tool/showlocks.c 9cc5e66d4ebbf2d194f39db2527ece92077e86ae627ddd233ee48e16e8142564
  F tool/speed-check.sh 615cbdf50f1409ef3bbf9f682e396df80f49d97ed93ed3e61c8e91fae6afde58
- P 35cd87063d1933b87bc2176f957ecd758d7d167e9473fa615e33caec3be14783
- R 746d9475007e84ed494c6df8218f252e
 -P 587ded6035a3ce91db81a29fe34ed30d0e59022cba6f107f25b04d034ef37ba9
 -R 831bdc39962e2b4ff60a753fe2bb6e80
++P c1ea064948ba08c4be209ad6efc2126a7367bcb06266ea35eb957bf2d4e2cb9f 270e17bba1d35f8c300844e75b2aa15f79a1ab62e40bc5e6bc9694902f8f7dde
++R 1546768fbbda9cf26d0f2836127121bd
++T +closed 270e17bba1d35f8c300844e75b2aa15f79a1ab62e40bc5e6bc9694902f8f7dde
  U drh
- Z e8621449358c788389d3aef6e8aa26e8
 -Z fbd73fea0049f831d8aafb6160e31d52
++Z 8bd06bc7fc2942f7b1a3d5039b41b801

diff --cc manifest.uuid
index de87faccc834063b0943e3e4033f7466128293c2,d6fb012a397201e85dd9ff78fb0797a51d7e2adc..52f49ddc1765ba49b2b6c143e01b48959c020961
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- c1ea064948ba08c4be209ad6efc2126a7367bcb06266ea35eb957bf2d4e2cb9f
 -270e17bba1d35f8c300844e75b2aa15f79a1ab62e40bc5e6bc9694902f8f7dde
++88baf1eb0706503214012520be4d872594ccc5b4c9674c44cc07b67ade2bfcf2