phy: initial commit for phy pib handling

This patch adds src/phy.c file. In this file should be the
implement the phy pib handling of the IEEE 802.15.4 standard.

In this patch we add handling to set channel and page according
channel/page number.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
mac: initial commit for mac pib handling

This patch adds a new mac.c file into src directory. In this
file we should implement all mac pib handling according the
IEEE 802.15.4 standard.

For this initial commit we support setting of the pan id of
IEEE 802.15.4 interface.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
gitignore: add phy and mac object files

Signed-off-by: Alexander Aring <alex.aring@gmail.com>