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.
This centralizes construction of the error message for an unclosed
logical block (if, foreach, etc.). We record the line at which each
block is opened so it can be reported in the error message.
When a function blocker decides to remove itself we previously removed
it at every return point from the C++ scope in which its removal is
needed. This teaches function blockers to transfer ownership of
themselves from cmMakefile to an automatic variable for deletion on
return. Since this removes blockers before they replay their commands,
we no longer need to avoid running blockers on their own commands.
