Merge of Wu's GSOC 09 branch (src.20090525.r4372.wu)

Main changes:
- COW optimization for safecopy.
- safemap, a grant-based interface for sharing memory regions between processes.
- Integration with safemap and complete rework of DS, supporting new data types
  natively (labels, memory ranges, memory mapped ranges).
- For further information:
  http://wiki.minix3.org/en/SummerOfCode2009/MemoryGrants

Additional changes not included in the original Wu's branch:
- Fixed unhandled case in VM when using COW optimization for safecopy in case
  of a block that has already been shared as SMAP.
- Better interface and naming scheme for sys_saferevmap and ds_retrieve_map
  calls.
- Better input checking in syslib: check for page alignment when creating
  memory mapping grants.
- DS notifies subscribers when an entry is deleted.
- Documented the behavior of indirect grants in case of memory mapping.
- Test suite in /usr/src/test/safeperf|safecopy|safemap|ds/* reworked
  and extended.
- Minor fixes and general cleanup.
- TO-DO: Grant ids should be generated and managed the way endpoints are to make
sure grant slots are never misreused.

kernel/system/Makefile

@@ -44,6 +44,7 @@ OBJECTS	= \
 	$(SYSTEM)(do_privctl.o) \
 	$(SYSTEM)(do_segctl.o) \
 	$(SYSTEM)(do_safecopy.o) \
+	$(SYSTEM)(do_safemap.o) \
 	$(SYSTEM)(do_sysctl.o) \
 	$(SYSTEM)(do_getksig.o) \
 	$(SYSTEM)(do_endksig.o) \
@@ -155,6 +156,9 @@ $(SYSTEM)(do_privctl.o):	do_privctl.c
 $(SYSTEM)(do_safecopy.o):	do_safecopy.c
 	$(CC) do_safecopy.c
 
+$(SYSTEM)(do_safemap.o):	do_safemap.c
+	$(CC) do_safemap.c
+
 $(SYSTEM)(do_sysctl.o):	do_sysctl.c
 	$(CC) do_sysctl.c