~ruther/vhdl-i2c

ref: b1f70489999e3922af2a934aa5a477a7b477484d vhdl-i2c/src d---------
tests: add startstop condition detector tests, fix behavior
fix: bugs in address detector
fix: compilation errors
feat: add i2c slave state entity
feat: add i2c misc entities
feat: add i2c rx, tx entities
feat: add utility entities

Delay, metastability filter, open drain buffer, synchronous edge detector