Ensure that split names are valid

Generate valid split names for resource splits.
Validate split names for features.

Change-Id: I3040438af0156778c2bd66ddeffdf62fe9dcc9fc
diff --git a/tools/aapt/ApkBuilder.h b/tools/aapt/ApkBuilder.h
index db23c84..0d7f06b 100644
--- a/tools/aapt/ApkBuilder.h
+++ b/tools/aapt/ApkBuilder.h
@@ -95,6 +95,10 @@
         return mDirName;
     }
 
+    const android::String8& getPackageSafeName() const {
+        return mPackageSafeName;
+    }
+
     bool isBase() const {
         return mIsBase;
     }
@@ -111,6 +115,7 @@
     const bool mIsBase;
     String8 mName;
     String8 mDirName;
+    String8 mPackageSafeName;
     std::set<OutputEntry> mFiles;
 };