GitLab

* feat: FindPython support

* refactor: rename to PYBIND11_FINDPYTHON

* docs: Caps fixes

* feat: NOPYTHON mode

* test: check simple call

* docs: add changelog/upgrade guide

* feat: Support Python3 and Python2

* refactor: Use targets in tests

* fix: support CMake 3.4+

* feat: classic search also finds virtual environments

* docs: some updates from @wjakob's review

* fix: wrong name for QUIET mode variable, reported by @skoslowski

* refactor: cleaner output messaging

* fix: support debug Python's in FindPython mode too

* fixup! refactor: cleaner output messaging

* fix: missing pybind11_FOUND and pybind11_INCLUDE_DIR restored to subdir mode

* fix: nicer reporting of Python / PyPy

* fix: out-of-order variable fix

* docs: minor last-minute cleanup

fix: include PYTHON_IS_DEBUG

- look for windows python lib when using mingw & msys
  - if not found, then look for system python lib as before

pybind11_add_module fails because FindPythonLibsNew.cmake try to link PythonXX.lib, but the first letter "p" should be lowercase.

This variable is a CMake community standard to set the C++
standard of a build. Document it in favor of the previous variable,
which stays as a legacy flag for existing projects.

https://cmake.org/cmake/help/v3.17/variable/CMAKE_CXX_STANDARD.html

Add Python 3.8 to considered versions in CMake for additional
hints.
https://cmake.org/cmake/help/v3.2/module/FindPythonLibs.html

On some linuxes, /usr/include belongs to GCC and the standard
libraries that work with clang are in /usr/lib/clang/8.0.0 or
some variation thereof.

This results in errors such as:

```
/../lib64/gcc/x86_64-pc-linux-gnu/8.3.0/../../../../include/c++/8.3.0/bits/cxxabi_init_exception.h:38:10: fatal error: 'stddef.h' file not found

```

during extraction.

Recent versions of clang.cindex include [code][1] that converts
the internal byte strings to python str for you.

  [1]: https://github.com/llvm-mirror/clang/blob/master/bindings/python/clang/cindex.py#L72