add new option to ApiCheck to look for new API methods

When 'newapi' option is needed, ApiCheck will be in "diff" mode:
* when classes are checked for consistency, newly added methods
  and constructors are kept in lists
* when packages are checked for consistency, newly added classes
  and classes with new API methods are kept in list
* when APIs are checked for consistency, newly added packages
  and pakages with new/modified classes are added
* the accumulated deltas are then exported in XML format

Change-Id: I3fed989e2836109e334c0e665639190196f14f4c
4 files changed