Move main() out of clatd.c.

This allows us to unit test methods that are in clatd.c.
Also simplify the build file, adding a defaults stanza and
grouping files in a filegroup so that both the code and the unit
test have the same source files.

Test: atest clatd_test
Test: builds, boots, 464xlat works
Change-Id: I544c3ee846abd3e38b80a2d9a4db5497fd9beb0c
9 files changed