fix warnings about unaligned loads from UBSAN

Use memcpy instead to ensure that we don't get warnings about
unaligned loads from UBSAN:

```
../3rdParty/jxrlib/image/decode/segdec.c:66:12: runtime error: load of misaligned address 0x7fc3a0544006 for type 'U32', which requires 4 byte alignment
0x7fc3a0544006: note: pointer points here
 01 01 a5 c0 b0 7c  0a 06 05 00 0c 14 10 c2  c0 30 80 38 72 41 ae 1a  8f 54 26 c2 9e f6 c1 25  a9 65
             ^
    #0 0x7fc3e137429a in _load4 ../3rdParty/jxrlib/image/decode/segdec.c:66
    #1 0x7fc3e13748b8 in _flushBit16 ../3rdParty/jxrlib/image/decode/segdec.c:80
    #2 0x7fc3e13749a6 in _getBit16 ../3rdParty/jxrlib/image/decode/segdec.c:86
    #3 0x7fc3e1385d75 in DecodeMacroblockDC ../3rdParty/jxrlib/image/decode/segdec.c:1224
    #4 0x7fc3e131924a in processMacroblockDec ../3rdParty/jxrlib/image/decode/strdec.c:412
    #5 0x7fc3e137207a in ImageStrDecDecode ../3rdParty/jxrlib/image/decode/strdec.c:4003
    #6 0x7fc3e126c0b2 in PKImageDecode_Copy_WMP ../3rdParty/jxrlib/jxrgluelib/JXRGlueJxr.c:1874
```

image/decode/segdec.c

@@ -63,7 +63,9 @@ static U32 _FORCEINLINE _load4(void* pv)
     v |= ((U32)((U16 *) pv)[1]) << 16;
     return _byteswap_ulong(v);
 #else // _M_IA64
-    return _byteswap_ulong(*(U32*)pv);
+    U32 v;
+    memcpy(&v, pv, sizeof(U32));
+    return _byteswap_ulong(v);
 #endif // _M_IA64
 #endif // _BIG__ENDIAN_
 }

image/sys/strcodec.c

@@ -694,7 +694,9 @@ U32 load4BE(void* pv)
     v |= ((U32)((U16 *) pv)[1]) << 16;
     return _byteswap_ulong(v);
 #else // _M_IA64
-    return _byteswap_ulong(*(U32*)pv);
+    U32 v;
+    memcpy(&v, pv, sizeof(U32));
+    return _byteswap_ulong(v);
 #endif // _M_IA64
 #endif // _BIG__ENDIAN_
 }