Switch minui over to C++.

Change-Id: I59e08a304ae514a3fdb6fab58721f11670bc1b01
diff --git a/minui/Android.mk b/minui/Android.mk
index 66dea74..52f0662 100644
--- a/minui/Android.mk
+++ b/minui/Android.mk
@@ -3,10 +3,10 @@
 
 LOCAL_SRC_FILES := \
     events.cpp \
-    graphics.c \
-    graphics_adf.c \
-    graphics_fbdev.c \
-    resources.c \
+    graphics.cpp \
+    graphics_adf.cpp \
+    graphics_fbdev.cpp \
+    resources.cpp \
 
 LOCAL_WHOLE_STATIC_LIBRARIES += libadf
 LOCAL_STATIC_LIBRARIES += libpng