Update pybind11

See merge request !191

Update Pybind11 to v2.9.2

Allow passing an XML file

See merge request !189

Adds command-line option -x to supply a castxml generated XML file to use
instead of generating it with pygccxml.

Also adds XML_INPUT option to CMake function autopybind11_add_module to supply
this XML file.

test commit

See merge request !190

Eigen::Ref pbr safety checks

See merge request !179

Configure cxx compiler version

See merge request !175

Reduce Binding Output

See merge request !176

partial support for substituting expanded template
insts and aliases declared in non yaml
declared namespaces

This partially reverts commit 8ad0a05e

See merge request !174

It maintains the warnings flag, but reverts the warning messages to using standard prints instead of using the warnings library.

Add flag for ignoring pygccxml warnings

Closes #195

See merge request !172

Add an print_warnings flag which will inform the warnings module to
ignore warnings which are set by pygccxml.

Change all print messages which contained warnings to use the warnings
module.

Fixes: #195