Improved ExperimentValue. Bug Fixes.

Breaking changes due to type of value being passed for ExperimentValue (object to pointer).

Fixed non-portable CMake code.

Updated README.md

Merge branch 'release/v2.8.2'

Merge branch 'release/v2.8.1'

Merge branch 'release/v2.8.0'

Removed need for a vcpkg patch file.

Merge branch 'develop'

Develop (#150)

* Use _WIN32 instead of WIN32 preprocessor macro (#138)

- _WIN32 is the recommended preprocessor macro
- Substitute occurrences of WIN32 with _WIN32 using:
  git grep -lw -e 'WIN32' -- | xargs sed -i -e 's/\<WIN32\>/_WIN32/g'

* Cleanup some compiler issues on MacOS. (#141)

In file include/celero/ThreadLocal.h:
* `thread_local` is a C++ keyword so using an #ifdef check for its
  existence is not reliable. Instead, check for C++11 support to
  determine if `thread_local` is already defined. See here
  https://stackoverflow.com/questions/5047971/how-do-i-check-for-c11-support.
* Also the check `#if __STDC_VERSION__ >= 201112` is not meaningful,
  since presumably Celero is being compiled with a C++ compiler, so it
  has been removed.

In file src/Memory.cpp:
* Added include for `<cstring>` so that `strlen` and `strncmp` are
  defined for Apple environment.

Fixes #140

* Made it easier to use the Fixed baseline properly with UDMs.

* Improving the "cost of pimpl" experiment.

* #148 Added UDM to the output file

Also remove Google Test submodule.

* Create codeql-analysis.yml (#149)

* Removed requirement for GTest in Travis.ci

* #143 Added clarification to README.md on Doxygen.

* Code Cleanup

* Copyright Update 2021

Co-authored-by: Wolfgang Stöggl <[email protected]>
Co-authored-by: jiverson002 <[email protected]>