Merge pull request #7908 from gebart/pr/cortexm-rm-estack

cpu/cc2538/vectors.c

cpu/cc26x0/vectors.c

cpu/cortexm_common/include/vectors_cortexm.h

cpu/ezr32wg/vectors.c

cpu/kinetis/include/vectors_kinetis.h

cpu/lm4f120/vectors.c

cpu/lpc1768/vectors.c

cpu/nrf51/vectors.c

cpu/nrf52/vectors.c

cpu/sam3/vectors.c

cpu/samd21/vectors.c

cpu/saml21/vectors.c

cpu/stm32f3/vectors.c

cpu/stm32l1/vectors.c

cpu/stm32l4/vectors.c