Add mechanism for adding new files to ojluni/annotations.

This change adds two new make targets which create empty stub files suitable
for copying into ojluni/annotations, which the developer can then annotate.

The instructions (and a description of the previously undocumented
mmodule subdirectory) are included in the README.

Bug: 64930165
Bug: 115746226
Test: Followed the steps added to the README
Change-Id: Iea070ffb97cd93731f24ba379fd3a38d0b70b9c6
2 files changed