Add backup size checking

Converted bootloader.cpp to TWRP and removed AOSP fstab parsing
from startup
diff --git a/Android.mk b/Android.mk
index 4fd182d..e13af68 100644
--- a/Android.mk
+++ b/Android.mk
@@ -20,7 +20,7 @@
 
 LOCAL_SRC_FILES := \
     recovery.cpp \
-    bootloader.cpp \
+    twbootloader.cpp \
     install.cpp \
     roots.cpp \
     ui.cpp \