(bionic doesn't include g++7 ppa)

Also fix use_example_configs

- Enable / disable interrupts with `__iSeiRetVal` / `__iCliRetVal`
- Add STM32F1 to Travis CI tests

Support env MARLIN_LANGS for user select generated language, and update doc; update script to generate dogm_font_data_ISO10646_1.h automatically.

Enable 6th-order jerk-controlled motion planning in real-time.
Only for 32bit MCUs. (AVR simply does not have enough processing power for this!)

- `M666` is static, not inline
- Disambiguate some stepper macros

- This status screen uses the ST7920 character generator to greatly
  reduce SPI traffic and MCU load when updating the status screen.

- Has been tested with the RepRapDiscount Full Graphics Smart Controller
  but should work with any LCD that uses an ST7920 or fully compatible
  controller.