lowpan_hdlc_adapter: New HAL adapter for wpantund

This tool is designed to quickly enable wpantund to use the ILowpanDevice
HAL, introduced in change Ib4a1ee35d1a02e3a38be406825bae3fdf9b0072f.

Long term, this capability should be built into wpantund, making this
tool obsolete.

This change also includes related updates to the product makefiles.

Bug: b/64090883
Change-Id: I9d7a80df20c69b8c335b88d984d9f8909d483fcd
8 files changed