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.

test/safecopy/system.conf

@@ -0,0 +1,34 @@
+
+service requestor
+{
+	system
+		SAFECOPYFROM
+		SAFECOPYTO
+		SAFEMAP
+		SAFEREVMAP
+		SAFEUNMAP
+		UMAP
+		PRIVCTL
+		SETGRANT
+		GETINFO
+		SYSCTL
+	;
+	uid	0;
+};
+
+service grantor
+{
+	system
+		SAFECOPYFROM
+		SAFECOPYTO
+		SAFEMAP
+		SAFEREVMAP
+		SAFEUNMAP
+		UMAP
+		PRIVCTL
+		SETGRANT
+		GETINFO
+		SYSCTL
+	;
+	uid	0;
+};