Hardcopy of pybind11 instead of using git submodules (#552)

* removed pybind as submodule
* added hardcopy of pybind11 2.10.0
* rename pybind11 folder to avoid conflicts when changing branch

Co-authored-by: Dhanya Thattil <dhanya.thattil@psi.ch>

libs/pybind/tests/env.py

@@ -0,0 +1,28 @@
+import platform
+import sys
+
+import pytest
+
+LINUX = sys.platform.startswith("linux")
+MACOS = sys.platform.startswith("darwin")
+WIN = sys.platform.startswith("win32") or sys.platform.startswith("cygwin")
+
+CPYTHON = platform.python_implementation() == "CPython"
+PYPY = platform.python_implementation() == "PyPy"
+
+
+def deprecated_call():
+    """
+    pytest.deprecated_call() seems broken in pytest<3.9.x; concretely, it
+    doesn't work on CPython 3.8.0 with pytest==3.3.2 on Ubuntu 18.04 (#2922).
+
+    This is a narrowed reimplementation of the following PR :(
+    https://github.com/pytest-dev/pytest/pull/4104
+    """
+    # TODO: Remove this when testing requires pytest>=3.9.
+    pieces = pytest.__version__.split(".")
+    pytest_major_minor = (int(pieces[0]), int(pieces[1]))
+    if pytest_major_minor < (3, 9):
+        return pytest.warns((DeprecationWarning, PendingDeprecationWarning))
+    else:
+        return pytest.deprecated_call()