Provide more configurable Serial.begin variants

[robertinant]

From @dronus on June 19, 2016 16:59

It would be nice if bitcount, stopbit and parity would be configurable by Serial.begin.

While Arduino libraries may be hacked to use different settings, the more complex controllers like MSP432 are using precompiled libraries and it is almost impossible to change those settings.
This is sad as some peripherial hardware require different settings.

For most UARTs used by HardwareSerial, this settings are easily applied.

Copied from original issue: energia/Energia#903

[robertinant]

From @rei-vilo on June 19, 2016 17:14

Linked to #835.