Tell editors that these are Makefiles (or fragments thereof).

Change-Id: I0c5e29ac750b9605b1e8f823d6998d31a933b7a4
diff --git a/Android.mk b/Android.mk
index 8cc23ce..1e25524 100644
--- a/Android.mk
+++ b/Android.mk
@@ -1,3 +1,4 @@
+# -*- mode: makefile -*-
 
 sqlite_jdbc_src_files := \
     src/main/native/sqlite_jni.c