Ref: #19499

* Change some functions to take `std::string` instead of
  `const char*` in the following classes: `cmMakeFile`, `cmake`,
  `cmCoreTryCompile`, `cmSystemTools`,  `cmState`, `cmLocalGenerator`
  and a few others.
* Greatly reduce using of `const char*` overloads for
  `cmSystemTools::MakeDirectory` and `cmSystemTools::RelativePath`.
* Remove many redundant `c_str()` conversions throughout the code.

Changes done via `clang-tidy` with some manual fine-tuning
for the variable naming and `auto` type deduction
where appropriate.

Per-source copyright/license notice headers that spell out copyright holder
names and years are hard to maintain and often out-of-date or plain wrong.
Precise contributor information is already maintained automatically by the
version control tool.  Ultimately it is the receiver of a file who is
responsible for determining its licensing status, and per-source notices are
merely a convenience.  Therefore it is simpler and more accurate for
each source to have a generic notice of the license name and references to
more detailed information on copyright holders and full license terms.

Our `Copyright.txt` file now contains a list of Contributors whose names
appeared source-level copyright notices.  It also references version control
history for more precise information.  Therefore we no longer need to spell
out the list of Contributors in each source file notice.

Replace CMake per-source copyright/license notice headers with a short
description of the license and links to `Copyright.txt` and online information
available from "https://cmake.org/licensing".  The online URL also handles
cases of modules being copied out of our source into other projects, so we
can drop our notices about replacing links with full license text.

Run the `Utilities/Scripts/filter-notices.bash` script to perform the majority
of the replacements mechanically.  Manually fix up shebang lines and trailing
newlines in a few files.  Manually update the notices in a few files that the
script does not handle.

Kitware Robot authored 8 years ago and Brad King committed 8 years ago

Run the `Utilities/Scripts/clang-format.bash` script to update
all our C++ code to a new style defined by `.clang-format`.
Use `clang-format` version 3.8.

* If you reached this commit for a line in `git blame`, re-run the blame
  operation starting at the parent of this commit to see older history
  for the content.

* See the parent commit for instructions to rebase a change across this
  style transition commit.

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.

ENH: add return and break support to cmake, also change basic command invocation signature to be able to return extra informaiton via the cmExecutionStatus class

ENH: Moved ExpandListVariables out of individual commands.  Argument evaluation rules are now very consistent.  Double quotes can always be used to create exactly one argument, regardless of contents inside.

ENH: Added reference to Copyright.txt.  Removed old reference to ITK copyright.  Changed program name to CMake instead of Insight in source file header.  Also removed tabs.

ENH: change InitialPass to take a const reference to the argument string, to avoid changes to the file cache