This fixes issue #580.

This fixes issue #585.

This fixes issue #547

Instead of hexadecimal, use (exact) decimal representation of floating
points to achieve compatibility with other graphml readers.

This fixes issue #570.

This fixes issue #551

This fixes issue #550.

This fixes issue #503.

This avoids a collapse with std::scoped_lock.

This fixes issue #511.

Fix m4 recipe for boost::context to work with boost >=1.68

See merge request count0/graph-tool!15

Numpy will use free() not delete, so we need to use malloc to avoid a
mismatch.

This fixes issue #579.

Call cairo.get_include() to find py3cairo.h

See merge request !16