Add kld to CATEGORIES.

Set SSP_UNSAFE.

Set IGNORE if the kernel sources are not found in SRC_BASE.

Define KMODDIR to /boot/modules by default, add it to PLIST_SUB and MAKE_ENV, and create it upon installation. If KMODDIR is set to /boot/kernel, it will be rewritten to /boot/modules. This prevents breaking packages when upgrading the kernel due to /boot/kernel being renamed to /boot/kernel.old in the process.

Handle cross-referencing kernel modules upon installation and deinstallation, using @kld.

If the debug argument is given, the port can install a debug version of the module into KERN_DEBUGDIR/KMODDIR. By default, KERN_DEBUGDIR is copied from DEBUGDIR and set to /usr/lib/debug. The framework will take care of creating and removing any required directories.