- Add cmMakefile methods IssueError and IssueWarning
  - Maintain an explicit call stack in cmMakefile
  - Include context/call-stack info in messages
  - Nested errors now unwind the call stack
  - Use new mechanism for policy warnings and errors
  - Improve policy error message
  - Include cmExecutionStatus pointer in call stack
    so that errors deeper in the C++ stack under
    a command invocation will become errors for the
    command