init: Implement exec support

Code copied from CM7 implementation by Steve Kondik

Change-Id: Ie8f11e9dc9e552aa7a4fe354995daaf8f0d99a11
core: allow radio users to access all rmnet* interface

Change-Id: Ibc3bf9654cf68362369422f82afe53ef86e3e710
Merge "init: Implement exec support" into alpha
Merge "core: allow radio users to access all rmnet* interface" into alpha