Fix XtraDB LPBug #714143 :

Windows native async io is disabled.

The patch uses completion ports for asynchronous IO notification , 
instead of formerly  used notification via event . This also removes
the limit of 64 async IOs per background IO thread (this limit was 
forced  by using WaitForMultipleObjects in previous AIO implementation)

CMakeLists.txt

@@ -59,7 +59,7 @@ IF (MSVC_VERSION GREATER 1400)
 ENDIF()
 
 
-SET(CMAKE_INSTALL_PREFIX "C:/MariaDB${MYSQL_BASE_VERSION}")
+SET(CMAKE_INSTALL_PREFIX "C:/MariaDB${MYSQL_BASE_VERSION}" CACHE PATH "Default installation directory")
 SET(INSTALL_ROOT "${CMAKE_INSTALL_PREFIX}")
 # Set standard options
 ADD_DEFINITIONS(-DHAVE_YASSL)

storage/innodb_plugin/handler/ha_innodb.cc

@@ -10916,12 +10916,12 @@ static MYSQL_SYSVAR_LONG(file_io_threads, innobase_file_io_threads,
 static MYSQL_SYSVAR_ULONG(read_io_threads, innobase_read_io_threads,
   PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_READONLY,
   "Number of background read I/O threads in InnoDB.",
-  NULL, NULL, 4, 1, 64, 0);
+  NULL, NULL, IF_WIN(1,4), 1, 64, 0);
 
 static MYSQL_SYSVAR_ULONG(write_io_threads, innobase_write_io_threads,
   PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_READONLY,
   "Number of background write I/O threads in InnoDB.",
-  NULL, NULL, 4, 1, 64, 0);
+  NULL, NULL, IF_WIN(1,4), 1, 64, 0);
 
 static MYSQL_SYSVAR_LONG(force_recovery, innobase_force_recovery,
   PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_READONLY,

storage/xtradb/include/os0file.h

@@ -152,8 +152,8 @@ log. */
 #define OS_FILE_LOG	256	/* This can be ORed to type */
 /* @} */
 
-#define OS_AIO_N_PENDING_IOS_PER_THREAD 32	/*!< Win NT does not allow more
-						than 64 */
+#define OS_AIO_N_PENDING_IOS_PER_THREAD 256	/*!< Windows might be able to handle
+more */
 
 /** Modes for aio operations @{ */
 #define OS_AIO_NORMAL	21	/*!< Normal asynchronous i/o not for ibuf

storage/xtradb/srv/srv0start.c

@@ -1274,13 +1274,7 @@ innobase_start_or_create_for_mysql(void)
 		break;
 	default:
 		/* On Win 2000 and XP use async i/o */
-		//os_aio_use_native_aio = TRUE;
-		os_aio_use_native_aio = FALSE;
-		fprintf(stderr,
-			"InnoDB: Windows native async i/o is disabled as default.\n"
-			"InnoDB:   It is not applicable for the current"
-			" multi io threads implementation.\n");
-		break;
+		os_aio_use_native_aio = TRUE;
 	}
 #endif
 	if (srv_file_flush_method_str == NULL) {
@@ -1320,11 +1314,6 @@ innobase_start_or_create_for_mysql(void)
 				  "async_unbuffered")) {
 		srv_win_file_flush_method = SRV_WIN_IO_UNBUFFERED;
 		os_aio_use_native_aio = TRUE;
-		srv_n_read_io_threads = srv_n_write_io_threads = 1;
-		fprintf(stderr,
-			"InnoDB: 'async_unbuffered' was detected as innodb_flush_method.\n"
-			"InnoDB:   Windows native async i/o is enabled.\n"
-			"InnoDB:   And io threads are restricted.\n");
 #endif
 	} else {
 		fprintf(stderr,