Remove flawed diagnostic mapping functions

These haven't been usable since the early return was accidentally removed some
years ago causing all cases to fall through to the !Enabled condition.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@200123 91177308-0d34-0410-b5e6-96231b3b80d8
ARCMigrate: Introduce proper diagnostics for TransformActions

This starts to switch ARCMT to use proper diagnostic messages. The old use was
based on incorrect example code from the documentation.

The logic of the previous report() functions has been retained to support any
external consumers that might be intercepting diagnostic messages through the
old interface.

Note that the change in test/Misc/warning-flags.c isn't a new warning without a
flag, rather one that was previously invisible to the test. Adding a flag might
be a good idea though.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@200124 91177308-0d34-0410-b5e6-96231b3b80d8
Remove buggy example code from the documentation

Instead point readers to the latest, correct example code in SVN until we find
a way to automatically include example sources into the documentation (or until
someone steps up to maintain these actively).

This ensures that the examples are up-to-date, buildable, and most of all that
readers don't pick up incorrect usage.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@200125 91177308-0d34-0410-b5e6-96231b3b80d8
Identify two more unsafe uses of getCustomDiagID()

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@200126 91177308-0d34-0410-b5e6-96231b3b80d8