Make use of built-in bswap32() and bswap16() functions in GCC/Clang for a

significant performance improvement there.

FossilOrigin-Name: 8bfcda3d10aec864d71d12a1248c37e4db6f8899

diff --cc manifest
index c106e26357f4ad6f1ca63b8f4cfad0539a730bd1,aa0967343bf7eb26cdef72b6340e15554953858b..52ea7d278e61e2e0606e55e2856f3afd21a00c4f
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Change\san\sunreachable\sbranch\sinto\san\sassert()\sin\ssqlite3PagerAcquire()\nand\soptimize\ssqlite3PcacheOpenSavepoint()\sby\sfactoring\sout\srarely\sused\scode\ninto\sa\ssubroutine.
- D 2015-06-30T11:07:32.245
 -C Only\suse\s<nowiki>__builtin_bswap16()</nowiki>\swith\sGCC\s4.8\sand\slater.
 -D 2015-06-30T14:01:20.529
++C Make\suse\sof\sbuilt-in\sbswap32()\sand\sbswap16()\sfunctions\sin\sGCC/Clang\sfor\sa\nsignificant\sperformance\simprovement\sthere.
++D 2015-06-30T15:10:29.855
  F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
  F Makefile.in 285a0a234ed7610d431d91671c136098c2bd86a9
  F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@@ -1364,7 -1364,7 +1364,8 @@@ F tool/vdbe_profile.tcl 67746953071a9f8
  F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
  F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
  F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
- P d9a0481ce0fd9824b1566f182d68ec46ef091b1b
- R 24b6e6de7d9b089958239ab689d72050
 -P 79ff36b7170c9e7e7a9935c8b9d1665867771087
++P b406b20ecdf0bff63c5c222fab11cb9acee86765 ce8177e3e64d2ac4cd5d9e7757cdd5fcecd7d0ea
+ R e9f634c6724f1e6a3b5c72453520bbb0
++T +closed ce8177e3e64d2ac4cd5d9e7757cdd5fcecd7d0ea
  U drh
- Z 9400732c29ac033e0975f1d6b596266c
 -Z f2b5d98d916a7a92a030423af1030c7f
++Z 3fa235f76195131887feff91c1f8744e

diff --cc manifest.uuid
index bc33da0418fd27b7a840b7d5308b40e2f09f73b1,818c8d4f8b1215d4ffd5bea942454f7ce6f789fe..c16cd14878273dd72b7776454db630067aa6adfc
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- b406b20ecdf0bff63c5c222fab11cb9acee86765
 -ce8177e3e64d2ac4cd5d9e7757cdd5fcecd7d0ea
++8bfcda3d10aec864d71d12a1248c37e4db6f8899