Print hal file package in exported headers.

The information is already technically contained in the header guard,
but pulling it out will make it make more sense for people unfamiliar with
hidl.

Command used to test:
hidl-gen -o system/core/include/system/graphics-base.h
-Lexport-header  -r android.hardware:hardware/interfaces
android.hardware.graphics.common@1.0

Bug: 33541458
Test: manual inspection of output
Change-Id: Ie291158285eeebfedb999230cf9846b802cde2cf
diff --git a/main.cpp b/main.cpp
index c3589f0..f365778 100644
--- a/main.cpp
+++ b/main.cpp
@@ -20,6 +20,7 @@
 #include "Scope.h"
 
 #include <hidl-util/Formatter.h>
+#include <hidl-util/StringHelper.h>
 #include <android-base/logging.h>
 #include <set>
 #include <stdio.h>
@@ -953,8 +954,8 @@
 
     Formatter out(file);
 
-    out << "// This file is autogenerated by hidl-gen. Do not edit manually."
-           "\n\n";
+    out << "// This file is autogenerated by hidl-gen. Do not edit manually.\n"
+        << "// Source: " << packageFQName.string() << "\n\n";
 
     std::string guard;
     if (forJava) {
@@ -963,7 +964,7 @@
         out.indent();
     } else {
         guard = "HIDL_GENERATED_";
-        guard += packageFQName.tokenName();
+        guard += StringHelper::Uppercase(packageFQName.tokenName());
         guard += "_";
         guard += "EXPORTED_CONSTANTS_H_";