New "lint" errors, split Android-specific logic.

We really encounter three classes of trouble: errors, warnings, and
lints.  See added docs about the differences between them.  Colorize
trouble output to make it easier to triage.

Since both auxiliary tags and linting are project-specific, factor
out the Android-specific versions of these, and only put them into
place when the "-android" argument is requested.

Add linting logic to identify possible docs trouble, such as
missing or misleading annotations.

Test: make -j32 offline-sdk-docs
Bug: 37526420
Change-Id: Id8b5b4e143f206e959ecde4655e877ee7723e3cd
9 files changed