maps4: make page monitoring /proc file optional

Make /proc/ page monitoring configurable

This puts the following files under an embedded config option:

/proc/pid/clear_refs
/proc/pid/smaps
/proc/pid/pagemap
/proc/kpagecount
/proc/kpageflags

[akpm@linux-foundation.org: Kconfig fix]
Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index bbd9b14..38338ed 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -337,6 +337,7 @@
  */
 #define PSS_SHIFT 12
 
+#ifdef CONFIG_PROC_PAGE_MONITOR
 struct mem_size_stats
 {
 	struct vm_area_struct *vma;
@@ -717,6 +718,7 @@
 	.llseek		= mem_lseek, /* borrow this */
 	.read		= pagemap_read,
 };
+#endif /* CONFIG_PROC_PAGE_MONITOR */
 
 #ifdef CONFIG_NUMA
 extern int show_numa_map(struct seq_file *m, void *v);