On 32-bit systems UINT32_MAX properties aren't handled correctly

[Zephyrus29]

** Description **
MQTT properties such as the session expiry are not handled correctly if they're set to UINT32_MAX. This is due to them being handled as an int instead of an unsigned int.

To Reproduce
On a 32-bit system set MQTTPROPERTY_CODE_SESSION_EXPIRY_INTERVAL to UINT32_MAX
Record the session expiry from the broker, it will be 0xFF

Expected behavior
Should pass up 0xFFFFFFFF instead of 0xFF

Additional context
Should use uint32_t instead of int in the properties struct

[icraggs]

Which structure? The MQTTProperty structure in MQTTProperties.h has them unsigned.

However, the MQTTProperties_getNumericValue function returns an int rather than an unsigned int.

[Zephyrus29]

I see this in MQTTProperty_write in writeInt4.

As that takes an int, it'll end up being -1 in writeInt4 so (-1/ 16777216) is 0 and same with the other functions in there.

I think either change that to unsigned int or to change it to (anInt >> 24) & 0xFF and so on for the rest of the values

[zhizhi-dev]

I have fixed this issue
#1327

[icraggs]

So I think that writeInt4 and readInt4 should definitely be changed to take and return unsigned ints respectively. I'll make that change.

@Zephyrus29 can you try out the PR from @zhizhi-dev and see if it works for you? Thanks.

[icraggs]

I've reverted Pr #1327 because of errors created.

writeInt4 and readInt4 have been changed to take and return an unsigned int, rather than an int, so that might help. That might work - if anyone can try it out I'd appreciate it (lack of 32-bit environment easy to get to).