update check_proc_mem; add doc page; speedup 5..10 times

check_proc_mem

@@ -67,11 +67,9 @@ EXAMPLE:
   $_self
       Check processes with initial memory values
 
-  $_self -d /data/mybackups
-      Check iso files a given directory
-    
-  $_self -d /data/mybackups -w 14 -c 28
-      Check iso files a given directory and customized limits
+  $_self -w 1000 -c 2000
+      Check processes consuming more than 1000 MB and mark those as critical
+      that use more than 2000 MB.
 
 EOF
 }