introduce new feature: BOOTLOADER_ADDITIONALMSDEVICEWAIT

Configure "BOOTLOADER_ADDITIONALMSDEVICEWAIT" to the number of
milliseconds the bootloader should delay its bootup, so
the pullups have time to charge up.

Signed-off-by: Stephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>
revise configuration selection and fix builds for 12MHz

Signed-off-by: Stephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>
fix: broken build with ATmega88A and ATmega168A caused by toolchain

Signed-off-by: Stephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>