Don't allow subclasses to just override dimensions or buffer details
directly and instead force them to go via methods. This allows us
to do sanity checks on the new values and catch bugs and attacks.

(cherry picked from commit 53f913a761)

Move the checks around to avoid missing cases where we might access
memory that is no longer valid. Also avoid touching the underlying
stream implicitly (e.g. via the destructor) as it might also no
longer be valid.

A malicious server could theoretically use this for remote code
execution in the client.

Issue found by Pavel Cheremushkin from Kaspersky Lab

(cherry picked from commit d61a767d68)

(cherry picked from commit 7ac36ad42f)

(cherry picked from commit 47c7de6008)

(cherry picked from commit 36454cfa88)

(cherry picked from commit bbbb67ee32)

(cherry picked from commit bae4f60b08)

(cherry picked from commit fb7667646f)

(cherry picked from commit eea96c4e40)

(cherry picked from commit 16abf6bcef)

(cherry picked from commit e1210592c9)

(cherry picked from commit 71b0d7c86c)

(cherry picked from commit 13b58d9206)

We need to examine the incoming PixelBuffer, not the previous one
(which might not even be valid).

fix test order in convertLF and convertCRLF

We need to check the buffer length before accessing the incoming
string. Probably not a problem in practice as there should be a
final null in most incoming strings.

Issue found by Pavel Cheremushkin from Kaspersky Lab.

They have very different purpose, so make things easier to work
with by having multiple directories.

Window hooks aren't working well on modern systems so switch the
default to polling until we can fix things.

The new order of test avoid ready invalid memory address in ca.buf

Do not return returncode indicating error when listing sessions

Implements support in both client and server for the extended
clipboard format first seen in UltraVNC. Currently only implements
text handling, but that is still an improvement as it extends the
clipboard from ISO 8859-1 to full Unicode.

In prepartion for better clipboard extensions that can send Unicode
data between the client and server.

Change the internal clipboard API to use a request based model in
order to be prepared for more advanced clipboard transfers.

We convert between UTF-8 and ISO 8859-1 (latin 1) in several places
so create some common routines for this.

We now filter incoming data, which means we can start assuming the
clipboard data is always null terminated. This allows us to clean
up a lot of the internal handling.

This is required by the protocol so we should make sure it is
enforced. We are tolerant of clients that violate this though and
convert incoming clipboard data.

It was unused and added complexity and bugs to the code. So let's
remove it rather than trying to clean up a function no one needed.

Makes it easier to see what is overloaded and what isn't.

We're usually white listed, but let's be a good citizen and formally
request the keyboard grab ability from the compositor.

We will log the exception, so avoid direct writes to stderr by
simply removing these log lines.