Support for SIMATIC HMI TP1500 Comfort

[koceka]

This change adds support for the SIEMENS SIMATIC HMI TP1500 Comfort industrial touch screen's VNC client.
This panel needed changes for the following unsupported behavior:

• Reports a bit depth of 32 bits - this change accepts and treats all 32 bit requests as 24 bits,
• Requests the Cursor pseudo-encoding when a user clicks the touch panel's screen - this change does not disconnect on such message received

[qmfrederik]

@koceka Thanks. The macOS build failure is unrelated, I'll see if I can get that fixed.
Looks like this PR is more about "not erroring out" rather than actually adding support for 32-bit color/cursor pseudo-encoding, right?
Are there any unit tests you could add?

[koceka]

@qmfrederik Correct, this modification is about not erroring out. I haven't expanded the unit tests but now that you ask I will definitely look into it. I plan adding these with the next contrib as we have a Siemens TP1200 and also some Beckhoff brand touch panels in house that I haven't tried connecting to yet.