meson: require 0.61.3

This removes the dependency of dbus-display on --enable-modules.  It also allows
cleanups in modinfo collection and allows moving C++ compiler detection to
meson.build.

Because it is now deprecated to use install_subdir to create an empty directory,
replace it with install_emptydir.

Updating the Meson submodule to 0.61.5 also removes the message

    WARNING: Broken python installation detected. Python files installed
    by Meson might not be found by python interpreter.

unless using system meson is forced with --meson.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/873
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/848


Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>