Improve the internal mechanism used to keep track of what kind of syncing

to do for WAL transaction commits and checkpoint operations.
Use the checkpoint-style of syncing to sync the header of a new
or restarted WAL file.

FossilOrigin-Name: e8d23afe8478e42779ec1dd602ca2d77d4f3c26c4d54f52112c5aaa928536538

diff --cc manifest
index bfb51fad1c3a69722c528cf06e5b27bccc21d076,cfd5eb0e6473f97282aaaeda7807ad1ee1b4c535..154d622e08f8aef2113270aada035e8b003b8860
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Avoid\sreturning\sduplicate\srows\sin\sexperimental\spragmas\s"pragma_list",\n"module_list"\sand\s"function_list".
- D 2017-08-25T09:17:14.786
 -C Update\sthe\smechanism\sused\sto\skeep\strack\sof\swhat\skind\sof\ssyncing\sto\sdo\sfor\nWAL\stransaction\scommits\sand\scheckpoint\soperations.\s\sUse\sthe\scheckpoint-style\nof\ssyncing\sto\ssync\sthe\sheader\sof\sa\snew\sor\srestarted\sWAL\sfile.
 -D 2017-08-25T01:14:43.498
++C Improve\sthe\sinternal\smechanism\sused\sto\skeep\strack\sof\swhat\skind\sof\ssyncing\nto\sdo\sfor\sWAL\stransaction\scommits\sand\scheckpoint\soperations.\s\nUse\sthe\scheckpoint-style\sof\ssyncing\sto\ssync\sthe\sheader\sof\sa\snew\nor\srestarted\sWAL\sfile.
++D 2017-08-25T11:44:51.174
  F Makefile.in c644bbe8ebe4aae82ad6783eae6b6beea4c727b99ff97568b847ced5e2ac7afb
  F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
  F Makefile.msc 25b154da7f0b3d4924f27378c1f8d006285b80811f1ccf3ed953dbebf6282136
@@@ -1651,7 -1650,10 +1651,8 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
--P 25292b9a4eb5efc7db551da0b3c9cfd7e79da1594ee14729de44090e188c2b2a
- R 7b2e7d0666727914b868e680cae90457
- U dan
- Z 2b958aabca575686d03fef3a95382582
 -R 0c45c0346ff1a3d7a9dbb07f83f4f723
 -T *branch * wal-sync-refactor
 -T *sym-wal-sync-refactor *
 -T -sym-trunk *
++P b79cc8dc88c8ae03daff1290fd650b2b0e6f673ec9d83be6a533a57172930190 bf65dae8d4297c57ac63228ccf0100f9fabf2fb600438c9f2e10a29c4b118168
++R 537f505d2d307d3df7ac5ca0ae8a4ab7
++T +closed bf65dae8d4297c57ac63228ccf0100f9fabf2fb600438c9f2e10a29c4b118168
+ U drh
 -Z 5b1634e4e5e7d2e25acb68caf19e0213
++Z f4c9090d66a1befc7247247744f54bd9

diff --cc manifest.uuid
index 98964c88d8c276de3abe8a53d0ea1ee1b3c60fa3,cfce901f7c50f3ef649c909ef1f51c0a8918faac..f317d7cf9803c6df89d3dd63e98c118527fb6f28
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- b79cc8dc88c8ae03daff1290fd650b2b0e6f673ec9d83be6a533a57172930190
 -bf65dae8d4297c57ac63228ccf0100f9fabf2fb600438c9f2e10a29c4b118168
++e8d23afe8478e42779ec1dd602ca2d77d4f3c26c4d54f52112c5aaa928536538