cpu/cortexm: added and use central yield_from_isr() function

doc: hashes and isrpipe doxygen fixes

cpu/sam3: reworked PWM driver

shell: fix strtok_r compile error

tools: static_tests.sh: rm dependency to 'riot' remote

cppcheck: grnc/netif/hdr fix cppcheck warnings

cppcheck: cpu/cc2538 reduce scope of variables

- create group for isrpipe instead of adding it to sys directly
- alter file description accordingly

- fix group membership
- improve description style

sys: refactor synchronous uart

tests/unittests: add stm32f3discovery to BOARD_INSUFFICIENT_MEMORY

travis: remove .travis.yml and build scripts

cpu/stm32f1: implement lpm + run without PLL

cpu/stm32(_common & f2): implement delay after RCC peripheral clock enable

cpu/saml21: removed unused saml21_periph.h

boards/avsextrem: fix u_int type in smb380 driver

drivers/bmp180: move bmp180 driver to saul auto init using the correct way

gnrc_priority_queue:  fix doxygen document.

example/microcoap_server: fix link local address

Implements workaround 1 (use __DSB()) proposed in the stm32 errata
It was possible to lose data when you configure a peripheral
right after enabling its clock

cpu/stm32x: unified PWM driver implementations

cpu/stm32f4: Add I2C low speed support to the stm32f4