Enable four sorting threads by default in the command-line shell.

FossilOrigin-Name: 1cab83577c814feb35b4fb91af0d52a9751d99bc

src/shell.c

@@ -3532,7 +3532,6 @@ static void main_init(struct callback_data *data) {
   sqlite3_config(SQLITE_CONFIG_LOG, shellLog, data);
   sqlite3_snprintf(sizeof(mainPrompt), mainPrompt,"sqlite> ");
   sqlite3_snprintf(sizeof(continuePrompt), continuePrompt,"   ...> ");
-  sqlite3_config(SQLITE_CONFIG_SINGLETHREAD);
 }
 
 /*

src/threads.c

@@ -28,7 +28,7 @@
 #include "sqliteInt.h"
 
 /********************************* Unix Pthreads ****************************/
-#if SQLITE_OS_UNIX && defined(SQLITE_MUTEX_PTHREADS)
+#if SQLITE_OS_UNIX && defined(SQLITE_MUTEX_PTHREADS) && SQLITE_THREADSAFE>0
 
 #define SQLITE_THREADS_IMPLEMENTED 1  /* Prevent the single-thread code below */
 #include <pthread.h>
@@ -85,7 +85,7 @@ int sqlite3ThreadJoin(SQLiteThread *p, void **ppOut){
 
 
 /********************************* Win32 Threads ****************************/
-#if SQLITE_OS_WIN && !SQLITE_OS_WINRT
+#if SQLITE_OS_WIN && !SQLITE_OS_WINRT && SQLITE_THREADSAFE>0
 
 #define SQLITE_THREADS_IMPLEMENTED 1  /* Prevent the single-thread code below */
 #include <process.h>

src/vdbesort.c

@@ -31,7 +31,7 @@ typedef struct FileWriter FileWriter;
 ** operations to be single-threaded.
 */
 #ifndef SQLITE_MAX_SORTER_THREAD
-# define SQLITE_MAX_SORTER_THREAD 1
+# define SQLITE_MAX_SORTER_THREAD 4
 #endif
 
 /*