doc: Fixup Handsfree API
hfp: Update for new HFP 1.7 values
hfp: Add enum for known HF Indicators
emulator: Improve SLC establishment logic
emulator: Fix CHLD=? not treated as part of SLC
emulator: Add +BIND implementation
emulator: Add +BIEV implementation
emulator: Extend BRSF bitmap

The current check of 8 bits is not enough with HFP 1.7
emulator: Enable HF Indicator feature
doc: Add 'hf-indicators' feature to Handsfree API
handsfree: Implement new Features property value
doc: Add Distracted Driving Reduction to Handsfree
hfp: Add initial SLC negotiation for HFP 1.7
handsfree: Add new driver method for HF indicators
handsfree: Skeleton implementation of DDR

Distracted Driving Reduction or Enhanced Safety is implemented using HF
indicator 0x0001
hfp: Add HF Indicators BRSF feature for 1.7

If HFP 1.7 client is used, enable the right BRSF feature
emulator: Refactor data types
hfp: Add implementation of +BIEV
include: Add HF Indicators related API
handsfree: Implement new HF indicators API