Handle context.newline correctly in tube.interactive()

The `context.newline` or `self.newline` variable isn't obeyed when typing in interactive mode. It is used when sending and receiving lines through `tube.sendline` though, causing a mismatch.

The receiving end of the `tube.interactive()` already has handling of newlines, but the sending side does not.

Example:
```python
from pwn import *
io = process('cat')
io.newline = b'\r\n'
io.sendline(b'auto')
io.interactive()
```

```
$ python testinteractive.py DEBUG
[x] Starting local process '/usr/bin/cat' argv=[b'cat']
[+] Starting local process '/usr/bin/cat' argv=[b'cat'] : pid 19060
[DEBUG] Sent 0x6 bytes:
    b'auto\r\n'
[*] Switching to interactive mode
[DEBUG] Received 0x6 bytes:
    b'auto\r\n'
auto
$ test
[DEBUG] Sent 0x5 bytes:
    b'test\n'
[DEBUG] Received 0x5 bytes:
    b'test\n'
test
```

The expected outcome would be to send `b'test\r\n'.

The same problem arises in non-term mode (`PWNLIB_NOTERM=1`), where stdin is read in binary mode causing the OS line seperators to come through. Correctly replacing them with the `context.newline` setting allows to use the interactive input on windows hosts as well, without constantly sending `\r\n`.

pwnlib/tubes/tube.py

@@ -4,6 +4,7 @@
 
 import abc
 import logging
+import os
 import re
 import six
 import string
@@ -852,7 +853,7 @@ def interactive(self, prompt = term.text.bold_red('$') + ' '):
         is much more usable, since we are using :mod:`pwnlib.term` to print a
         floating prompt.
 
-        Thus it only works in while in :data:`pwnlib.term.term_mode`.
+        Thus it only works while in :data:`pwnlib.term.term_mode`.
         """
 
         self.info('Switching to interactive mode')
@@ -879,11 +880,21 @@ def recv_thread():
 
         try:
             while not go.isSet():
+                os_linesep = os.linesep.encode()
                 if term.term_mode:
                     data = term.readline.readline(prompt = prompt, float = True)
                 else:
                     stdin = getattr(sys.stdin, 'buffer', sys.stdin)
-                    data = stdin.read(1)
+                    data = b''
+                    if sys.stdin.isatty():
+                        while not data.endswith(os_linesep):
+                            new_byte = stdin.read(1)
+                            if not new_byte:
+                                break
+                            data += new_byte
+                    else:
+                        data = stdin.read(1)
+                data = data.replace(os_linesep, self.newline)
 
                 if data:
                     try: