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/libraries/kutil/memory.cpp

@@ -25,4 +25,13 @@ memcpy(void *dest, void *src, size_t n)
 	return d;
 }
 
+uint8_t
+checksum(const void *p, size_t len, size_t off)
+{
+	uint8_t sum = 0;
+	const uint8_t *c = reinterpret_cast<const uint8_t *>(p);
+	for (int i = off; i < len; ++i) sum += c[i];
+	return sum;
+}
+
 } // namespace kutil

src/libraries/kutil/memory.h

@@ -66,4 +66,10 @@ inline T* mask_pointer(T *p, addr_t mask)
 	return reinterpret_cast<T *>(reinterpret_cast<addr_t>(p) & ~mask);
 }
 
+/// Do a simple byte-wise checksum of an area of memory.
+/// \arg p    The start of the memory region
+/// \arg len  The number of bytes in the region
+/// \arg off  An optional offset into the region
+uint8_t checksum(const void *p, size_t len, size_t off = 0);
+
 } // namespace kutil