Multiple above-minor updates.

- fixed is_err(x), was evaluating x twice, resulting in calling a
function x twice.

- Divided task initialisation into multiple parts.
- MM0 now creates a tcb for itself and maintains memory regions of its own.
- MM0's tcb is used for mmapping other tasks' regions. MM0 mmaps and prefaults
  those regions, instead of the typical mmap() and fault approach used by
  non-pager tasks.
  For example there's an internal shmget_shmat() path to map in other tasks'
  shm utcbs. Those mappings are then prefaulted into mm0's address space using
  the default fault handling path.

- FS0 now reads task data into its utcb from mm0 via a syscall.
  FS0 shmat()s to utcbs of other tasks, e.g. mm0 and test0.

  FS0 then crashes, that is to be fixed and where this commit is left last.

include/l4/macros.h

@@ -78,7 +78,14 @@
 /* Functions who may either return a pointer or an error code can use these: */
 #define PTR_ERR(x)		((void *)(x))
 /* checks up to -1000, the rest might be valid pointers!!! E.g. 0xE0000000 */
-#define IS_ERR(x)		((((int)(x)) < 0) && (((int)(x) > -1000)))
+// #define IS_ERR(x)		((((int)(x)) < 0) && (((int)(x) > -1000)))
+#if !defined(__ASSEMBLY__)
+#define IS_ERR(x)	is_err((int)(x))
+static inline int is_err(int x)
+{
+	return x < 0 && x > -0x1000;
+}
+#endif
 
 /* TEST: Is this type of printk well tested? */
 #define BUG()			{do {								\