Replace system("cat") and system("dd") with C implementation

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>

Changelog

@@ -5,7 +5,8 @@
 	- drop system("rm -f") to clean /tmp, its a fresh mounted tmpfs
 	- write ACPI sleep state to /sys/power/state instead of
 	  /proc/acpi/sleep (Metalshark)
-	- use direct calls to set loopback instead of fork ifconfig
+	- use direct calls to set loopback instead of system("ifconfig")
+	- replace system("cat") and system("dd") with C implementation
 
 0.1 (20081214)
 	- initial release