.mov and .png open crash

[liupf1205]

When I was cross-compiling and using this library, I found that reading XMP metadata from .mov and .png files could cause crashes. Therefore, I added the following code between lines 70 and 71 in ISOBaseMedia_Support.cpp:

#if defined(_MSC_VER)
    _ReadWriteBarrier();
#elif defined(__GNUC__) || defined(__clang__)
    asm volatile("" ::: "memory");
#endif

And added the following code before line 232 in PNG_Support.cpp:

if (tempBuffer + 8 > bufferLimit) {
    break;
}

Do you approve of my changes?
I look forward to your response. Thank you.