Return value of XLogInsertRecord() for XLOG_SWITCH record

Hi,

I find that the return value of XLogInsertRecord() for XLOG_SWITCH record
is inconsistent with other records.

For XLOG_SWITCH record:

```
		/*
		 * Even though we reserved the rest of the segment for us, which is
		 * reflected in EndPos, we return a pointer to just the end of the
		 * xlog-switch record.
		 */
		if (inserted)
		{
			EndPos = StartPos + SizeOfXLogRecord;
			if (StartPos / XLOG_BLCKSZ != EndPos / XLOG_BLCKSZ)
			{
				uint64		offset = XLogSegmentOffset(EndPos, wal_segment_size);

				if (offset == EndPos % XLOG_BLCKSZ)
					EndPos += SizeOfXLogLongPHD;
				else
					EndPos += SizeOfXLogShortPHD;
			}
		}
```

It is equivalent to XLogBytePosToRecPtr(), but all other records use XLogBytePosToEndRecPtr().

No actual problem found yet, but I think it's better to keep them consistent. Thoughts?

--
Regards,
ChangAo Chen