physmem.c: align memory to word and page size

- physmem.c (align_sbrk): align the end of the data segment
- physmem.c (calloc_phys_vec): align the line pointer vector to a machine
  word, just in case
- physmem.c (calloc_phys_vec): crudely align the line buffers within
  pages, to avoid page-crossing within a line (yes, this does reduce
  noise)

ubb-vga/physmem.c

@@ -21,13 +21,25 @@
  */
 
 
+static void align_brk(int alignment)
+{
+	unsigned long addr;
+
+	addr = (unsigned long) sbrk(0);
+	sbrk(alignment-(addr % alignment));
+}
+
+
 void **calloc_phys_vec(size_t n, size_t size)
 {
 	void **vec;
 	int i;
 
+	align_brk(sizeof(void *));
 	vec = sbrk(sizeof(void *)*n);
+
 	for (i = 0; i != n; i++) {
+		align_brk(512);	/* crude page alignment */
 		vec[i] = sbrk(size);
 		memset(vec[i], 0, size);
 	}