Add basic lsof command

Basic "list open files" command.

Supports reading all processes for their "exe", "cwd", "root", and "fd"
entries.

Change-Id: I2e2f0911dd65a1993aa1ce9f51222bf264a9d68d
diff --git a/toolbox/Android.mk b/toolbox/Android.mk
index 9349276..588dac0 100644
--- a/toolbox/Android.mk
+++ b/toolbox/Android.mk
@@ -53,7 +53,8 @@
 	uptime \
 	vmstat \
 	nandread \
-	ionice
+	ionice \
+	lsof
 
 LOCAL_SRC_FILES:= \
 	toolbox.c \