Make the SQLITE_DEFAULT_SYNCHRONOUS and SQLITE_DEFAULT_WAL_SYNCHRONOUS
values zero-based to agree with PRAGMA synchronous.

FossilOrigin-Name: 592d2104361500e5002783ba329a2609389c57b9
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index a49601e..741caec 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1006,10 +1006,23 @@
 #include "mutex.h"
 
 /*
-** Default synchronous levels
+** Default synchronous levels.
+**
+** Note that (for historcal reasons) the PAGER_SYNCHRONOUS_* macros differ
+** from the SQLITE_DEFAULT_SYNCHRONOUS value by 1.
+**
+**           PAGER_SYNCHRONOUS       DEFAULT_SYNCHRONOUS
+**   OFF           1                         0
+**   NORMAL        2                         1
+**   FULL          3                         2
+**   EXTRA         4                         3
+**
+** The "PRAGMA synchronous" statement also uses the zero-based numbers.
+** In other words, the zero-based numbers are used for all external interfaces
+** and the one-based values are used internally.
 */
 #ifndef SQLITE_DEFAULT_SYNCHRONOUS
-# define SQLITE_DEFAULT_SYNCHRONOUS PAGER_SYNCHRONOUS_FULL
+# define SQLITE_DEFAULT_SYNCHRONOUS (PAGER_SYNCHRONOUS_FULL-1)
 #endif
 #ifndef SQLITE_DEFAULT_WAL_SYNCHRONOUS
 # define SQLITE_DEFAULT_WAL_SYNCHRONOUS SQLITE_DEFAULT_SYNCHRONOUS