This converts the CMake license to a pure 3-clause OSI-approved BSD
License. We drop the previous license clause requiring modified
versions to be plainly marked. We also update the CMake copyright to
cover the full development time range.
- 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