Use Dekker double-precision floating point to do the value normalization

step in sqlite3FpDecode() for systems on which "long double" is 8 bytes or
less.

FossilOrigin-Name: 51f492b440728151ce64168d5436ba87ca60d84b89408e47c593fa731355afe4

diff --cc manifest
index 60a8a88fd4a84b60d41203c88831d9690da264e6,7130835d4e2407400b2149bbb18853552fa5ab39..fd10ee48998cbeba328b573b5d4e8a4958d7bd1d
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C This\scheck-in\sadds\sthe\suse\sof\s"long\sdouble"\sto\ssqlite3FpDecode()\swhich\swhen\nrun\son\sx86\susing\sa\scompiler\sthat\stranslates\s"long\sdouble"\sinto\sbinary80,\ncauses\sall\slegacy\stests\sto\spass.\s\sBut\son\sa\ssystem\swhere\s"long\sdouble"\sis\sjust\nan\salias\sfor\s"double",\ssome\sof\sthe\stests\sare\sstill\sfailing.
- D 2023-07-01T20:21:27.087
 -C Final\sclean-up\sof\sthe\sidea\sof\susing\sDekker\sdouble-precision\sfloating\ncomputations\sto\simprove\saccuracy.
 -D 2023-07-03T11:39:38.542
++C Use\sDekker\sdouble-precision\sfloating\spoint\sto\sdo\sthe\svalue\snormalization\nstep\sin\ssqlite3FpDecode()\sfor\ssystems\son\swhich\s"long\sdouble"\sis\s8\sbytes\sor\nless.
++D 2023-07-03T11:44:15.056
  F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
  F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
  F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@@ -2041,8 -2041,8 +2041,9 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P 07eab52e0801bb0e4743b304a06ad16e18cdf8eaa18c0faf8d47a1f5d8576ea0
- R c4051b06b266c29a490b4cec354913fc
 -P 25d1ad6df1ed460c2cc9f32e8a5106e121ae502044f83abf431c1d5b3879eb56
++P ce06982f880339cf46704e95c907249827c3e44af2b9420005200ca8abd3f371 40285d631072b79aba39cc20d4b217bdf0069f29ac9902cb97dec28d3e4cde11
+ R 8a559af6860b1623fc9d9f5fb9393b11
++T +closed 40285d631072b79aba39cc20d4b217bdf0069f29ac9902cb97dec28d3e4cde11
  U drh
- Z 95eef79511e3e10371b4b76031a5a06d
 -Z 48672189b786297b4026c7966b4eccaa
++Z 98f04f31ed955532d376706d5d138150
  # Remove this line to create a well-formed Fossil manifest.

diff --cc manifest.uuid
index d2f8b9d453ee4fef06db608b4191a3fed5fa71f0,7757e469cd834faa97a05892047e0bed5a6a59e3..b3071eda1b7cfc43838b05e325e38673235ddc81
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- ce06982f880339cf46704e95c907249827c3e44af2b9420005200ca8abd3f371
 -40285d631072b79aba39cc20d4b217bdf0069f29ac9902cb97dec28d3e4cde11
++51f492b440728151ce64168d5436ba87ca60d84b89408e47c593fa731355afe4