AAPT2: Allow compatible duplicate Attributes

If a resource XML file defines two compatible Attributes, they should
be merged without throwing an error. Ex:

<declare-styleable>
  <attr name="conflict" format="string" />
</declare-styleable>

<declare-styleable>
  <attr name="conflict" format="string|reference" />
</declare-styleable>

In this case, string|reference and string are the same, so these should
merge correctly.

Bug: 65699599
Test: make aapt2_tests
Test: make AaptBasicTest
Change-Id: I7b0f956d2332f7f0b458acd59ca0a606b2cfdf95
diff --git a/tools/aapt2/ResourceTable.h b/tools/aapt2/ResourceTable.h
index eaa2d0b..95e30c4 100644
--- a/tools/aapt2/ResourceTable.h
+++ b/tools/aapt2/ResourceTable.h
@@ -81,10 +81,7 @@
   DISALLOW_COPY_AND_ASSIGN(ResourceConfigValue);
 };
 
-/**
- * Represents a resource entry, which may have
- * varying values for each defined configuration.
- */
+// Represents a resource entry, which may have varying values for each defined configuration.
 class ResourceEntry {
  public:
   // The name of the resource. Immutable, as this determines the order of this resource