SLIP layer for supporting packet framing in HCI transport.

This module implements SLIP packet framing as described in the Bluetooth Core Specification 4.0, Volume 4, Part D, Chapter 3 SLIP Layer.

SLIP framing ensures that all packets sent on the UART are framed as: <0xC0> SLIP packet 1 <0xC0> <0xC0> SLIP packet 2 <0xC0>.

The SLIP layer uses events to notify the upper layer when data transmission is complete and when a SLIP packet is received.