Initial ramdisk support

- Create initrd library to support definitions and loading
- Allow tools compiled for the host machine to be built by wscript
- Create makerd tool to build initrd from manifest
- Move screenfont to initrd, so don't load framebuffer initially

src/kernel/wscript

@@ -15,7 +15,7 @@ def build(bld):
         name = 'kernel',
         includes = '.',
         target = bld.env.KERNEL_FILENAME,
-        use = 'kutil',
+        use = ['kutil', 'initrd'],
         linkflags = "-T {}".format(lds),
     )