Add reasonable package path defaults.

Test: `hidl-gen -Lhash android.hardware.tests.foo@1.0` from anywhere in the source tree
Change-Id: I70d9333f32f1b3dbe0d0ebcc4956f4ae547e1e51
diff --git a/Coordinator.h b/Coordinator.h
index 703ef6f..1d52fa4 100644
--- a/Coordinator.h
+++ b/Coordinator.h
@@ -44,6 +44,9 @@
         return mRootPath;
     }
 
+    // adds path only if it doesn't exist
+    void addDefaultPackagePath(const std::string& root, const std::string& path);
+
     // Attempts to parse the interface/types referred to by fqName.
     // Parsing an interface also parses the associated package's types.hal
     // file if it exists.