[PATCH] msxml3: Fix a memory leak (Valgrind).

[阿杰]

==1461== 8 bytes in 1 blocks are possibly lost in loss record 178 of 3,995
==1461==    at 0x7BC6F0DA: notify_alloc (heap.c:260)
==1461==    by 0x7BC731BB: RtlAllocateHeap (heap.c:1725)
==1461==    by 0x7B04CEC2: LocalAlloc (memory.c:606)
==1461==    by 0x7B04CD6A: GlobalAlloc (memory.c:570)
==1461==    by 0x5D9FC30: CreateStreamOnHGlobal (hglobalstream.c:600)
==1461==    by 0x20580F06: domdoc_load_from_stream (domdoc.c:780)