aidl: Separate aidl logic into its own static library

Compile aidl's logic into a static library that can be
linked against both the unittest binary and the executable. Validate
that this is working by writing a basic unittest against options
parsing.

Provide default values for Options struct members.  These were
previously taking on values according to the the bits in the memory
allocated to hold them for preprocessed inputs.

Bug: 23516947
Change-Id: Ib57cd7f473995f7851d788deac39f9c4d9018e8f
Test: compiles and unittests pass