Merge the latest 3.8.4 tweaks from trunk.

FossilOrigin-Name: 1ed463d91866182fbc884fb88770717ee5bf33ce

src/vdbe.c

@@ -28,7 +28,7 @@
 ** pointer to the string or blob, not the content.  If the original
 ** is changed while the copy is still in use, the string or blob might
 ** be changed out from under the copy.  This macro verifies that nothing
-** like that every happens.
+** like that ever happens.
 */
 #ifdef SQLITE_DEBUG
 # define memAboutToChange(P,M) sqlite3VdbeMemAboutToChange(P,M)
@@ -681,6 +681,11 @@ int sqlite3VdbeExec(
 ** The next instruction executed will be 
 ** the one at index P2 from the beginning of
 ** the program.
+**
+** The P1 parameter is not actually used by this opcode.  However, it
+** is sometimes set to 1 instead of 0 as a hint to the command-line shell
+** that this Goto is the bottom of a loop and that the lines from P2 down
+** to the current line should be indented for EXPLAIN output.
 */
 case OP_Goto: {             /* jump */
   pc = pOp->p2 - 1;
@@ -2176,8 +2181,8 @@ case OP_BitNot: {             /* same as TK_BITNOT, in1, out2 */
 **
 ** Check if OP_Once flag P1 is set. If so, jump to instruction P2. Otherwise,
 ** set the flag and fall through to the next instruction.  In other words,
-** this opcode causes all following up codes up through P2 (but not including
-** P2) to run just once and skipped on subsequent times through the loop.
+** this opcode causes all following opcodes up through P2 (but not including
+** P2) to run just once and to be skipped on subsequent times through the loop.
 */
 case OP_Once: {             /* jump */
   assert( pOp->p1<p->nOnceFlag );