Add the sqlite3_status64() interface. Make the new interface and the legacy

sqlite3_status() both atomic and threadsafe.  Check threadsafety using
assert()s.

FossilOrigin-Name: 1ce8e8fa4b866aafa12b1da0eb4d02321af9293e

src/sqlite.h.in

@@ -1550,7 +1550,7 @@ struct sqlite3_mem_methods {
 **   <li> [sqlite3_memory_used()]
 **   <li> [sqlite3_memory_highwater()]
 **   <li> [sqlite3_soft_heap_limit64()]
-**   <li> [sqlite3_status()]
+**   <li> [sqlite3_status64()]
 **   </ul>)^
 ** ^Memory allocation statistics are enabled by default unless SQLite is
 ** compiled with [SQLITE_DEFAULT_MEMSTATUS]=0 in which case memory
@@ -6305,7 +6305,7 @@ int sqlite3_test_control(int op, ...);
 /*
 ** CAPI3REF: SQLite Runtime Status
 **
-** ^This interface is used to retrieve runtime status information
+** ^These interfaces are used to retrieve runtime status information
 ** about the performance of SQLite, and optionally to reset various
 ** highwater marks.  ^The first argument is an integer code for
 ** the specific parameter to measure.  ^(Recognized integer codes
@@ -6319,19 +6319,22 @@ int sqlite3_test_control(int op, ...);
 ** ^(Other parameters record only the highwater mark and not the current
 ** value.  For these latter parameters nothing is written into *pCurrent.)^
 **
-** ^The sqlite3_status() routine returns SQLITE_OK on success and a
-** non-zero [error code] on failure.
+** ^The sqlite3_status() and sqlite3_status64() routines return
+** SQLITE_OK on success and a non-zero [error code] on failure.
 **
-** This routine is threadsafe but is not atomic.  This routine can be
-** called while other threads are running the same or different SQLite
-** interfaces.  However the values returned in *pCurrent and
-** *pHighwater reflect the status of SQLite at different points in time
-** and it is possible that another thread might change the parameter
-** in between the times when *pCurrent and *pHighwater are written.
+** If either the current value or the highwater mark is too large to
+** be represented by a 32-bit integer, then the values returned by
+** sqlite3_status() are undefined.
 **
 ** See also: [sqlite3_db_status()]
 */
 int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag);
+int sqlite3_status64(
+  int op,
+  sqlite3_int64 *pCurrent,
+  sqlite3_int64 *pHighwater,
+  int resetFlag
+);
 
 
 /*