sys: use typedef for `struct bloom_t`
`bloom_t` is defined as a struct.
`_t` can mislead the user to think of bloom_t
as a typedef (see our coding conventions) instead of a struct.
Thus, I modified `struct bloom_t` to be a *typedefed* struct.

Another solution would be to rename bloom_t to sth. like bloom_s
everywhere and use `struct bloom_s` instead of `bloom_t`.
doc: add license headers to some .h files
cpu/boards: completed GPIO driver for sam3x8e

- adjusted peripheral conf for udoo and arduino-due
- added gpio_init_int()
- added interrupt service routines
- fixed gpio_read()
- added clock enable for gpio_init_in()
Merge pull request #1677 from LudwigOrtmann/headers

doc: add license headers to some .h files
board/yunjia-nrf5182: adjusted openocd.cfg
Merge pull request #1684 from haukepetersen/fix_yunjia_openocd

board/yunjia-nrf51822: adjusted openocd.cfg
cpu/nrf51822: adjusted default stack sizes
Merge pull request #1685 from haukepetersen/fix_nrf_stacksizes

cpu/nrf51822: adjusted default stack sizes
Merge pull request #1679 from cgundogan/bloom_t_as_typedef

sys: use typedef for `struct bloom_t`
Merge pull request #1486 from haukepetersen/fix_sam3x_finish_gpio

cpu/boards: completed GPIO driver for sam3x8e
added spark core board