doc: mark legacy adc API as deprecated
drivers: mark adc.h as legacy
cpu: use adc_legacy.h where appropriate
cpu/mc1322x: rename adc header to mc1322x-adc
boards, sys: purge feuerware_radios

* `feuerware_radios` is unused, remove from `radio.h` header
* FEUERWARE_CONF_NUM_RADIOS is superfluous without it, remove all occurrences
core,sys: fix storage types for irq API usage

* should not have any effect as long as `unsigned` and `int` are compatible
* also fix two cosmetic `unsigned int` -> `unsigned` for consistency
drivers/adc_legacy: add copyright, author
cpu/mc1322x: fix mc1322x-adc.h license
cpu/mc1322x: fix mc1322x-adc.h cpp compatability
Merge pull request #1882 from LudwigOrtmann/disableIRQ-type

core,sys: fix storage types for irq API usage
Merge pull request #1881 from LudwigOrtmann/purge_feuerware_radio

boards, sys: purge feuerware_radios
Merge pull request #1877 from LudwigOrtmann/adc_legacy

ADC legacy