uncrypt: Switch to C++

Also apply some trivial changes like int -> bool and clean-ups.

Change-Id: I5c6c42d34965305c394f4f2de78487bd1174992a
(cherry picked from commit 381f455cac0905b023dde79625b06c27b6165dd0)
diff --git a/uncrypt/Android.mk b/uncrypt/Android.mk
index 878d275..d832d97 100644
--- a/uncrypt/Android.mk
+++ b/uncrypt/Android.mk
@@ -16,7 +16,7 @@
 
 include $(CLEAR_VARS)
 
-LOCAL_SRC_FILES := uncrypt.c
+LOCAL_SRC_FILES := uncrypt.cpp
 
 LOCAL_MODULE := uncrypt