add test-data.mk

splits the test sources (test.mk) and the test data.

Change-Id: Id614cfe68bfbc09b0e429a37a21ec7a9dcdfadc6
test-data.mk: add some sectional comments

+ sort

Change-Id: Ib503037376368cec0cf57cbedeb215ab0eac8304
Merge changes Ib5030373,Id614cfe6

* changes:
  test-data.mk: add some sectional comments
  add test-data.mk