GUACAMOLE-2237: Pasting multiline text via browser menu produces sing…

[bbennett-ks]

There are 3 separate issues:

• SSH/Telnet (browser paste): Guacamole normalizes line endings to LF and types them 0xFF0A. The terminal handler sends this as 0x0A, which works on Linux/macOS but is ignored by Windows SSH.
• RDP (browser paste): Similarly, Guacamole sends 0xFF0A but RDP has no scan code for LF so it falls through to UnicodeKeyboardEvent(), which maps it to 'J'.
• SSH/Telnet (right-click and Ctrl+Shift+V paste): Clipboard bytes are sent directly to stdin. Keyboard emulation CRLF and LF to \n, which Windows SSH ignores.

The fixes for each:

• SSH/Telnet (browser paste): Send \x0D (CR) instead of \x0A for keysym 0xFF0A.
• RDP (browser paste): Remap keysym 0xFF0A → 0xFF0D (Return) before keymap lookup.
• SSH/Telnet (right-click and Ctrl+Shift+V paste): Convert \n → \r at paste time.

This standardizes multiline paste behavior across platforms (Linux, macOS, Windows) and paste mechanisms (browser paste via simulated keystrokes and clipboard paste via Ctrl+V/right-click) for SSH, Telnet, and RDP.