Improvements to asserts to enforce magic numbers in the wal-index format.

Also improve automatic configure and make builds on legacy PPC iBooks.

FossilOrigin-Name: 87b8d47889f1990442aa90398614656658207085d064381074f72bda9bdcbfa5

diff --cc manifest
index 9a4cb795d9183452efbfb7fd1f76006b3cfa0d6d,08aa89e51f73b62b9cd077abae8444e0ccc53492..2adaf55f144891f4b0d5218ea11e6dd9d0386b34
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Remove\sALWAYS()\smacros\sthat\scan\sbe\strue\sif\sthe\sinternal\stest\sfunction\nimplies_nonnull_row()\sis\sused\sin\sthe\sresult\sset\sof\sa\squery\sand\scontains\ncomparison\soperator\sagainst\sa\scomputed\scolumn.\ndbsqlfuzz\s4c34db5bff6247f33ee49e341a1f3018e72be0a0.
- D 2021-07-29T00:33:20.860
 -C Complete\swarning-free\sbuild\son\sold\sPPC\siBook.
 -D 2021-07-29T17:23:23.932
++C Improvements\sto\sasserts\sto\senforce\smagic\snumbers\sin\sthe\swal-index\sformat.\nAlso\simprove\sautomatic\sconfigure\sand\smake\sbuilds\son\slegacy\sPPC\siBooks.
++D 2021-07-29T17:31:40.386
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  F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@@ -1920,7 -1920,7 +1920,8 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
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diff --cc manifest.uuid
index 7ce3f9f163628ddc5fb1316f69c7c0ec3cd39171,843b94000a3f68d604e607acecf359cc61dbcfa1..3b5473b5ca6e54a89a0502dde5e49152d54cdc5a
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 4d1dbfa35c7dc0f09321b2e274a00e506f4ca65322454652d5891d815a6966d3
 -ef2a0850394b1c6c1fc84b26694a3712ae1e50d52bb78fea2ec40148a7d833de
++87b8d47889f1990442aa90398614656658207085d064381074f72bda9bdcbfa5