Yet another backend for hidl-gen, this one generates a C-compatible header file

containing those enum types annotated in the package like so:

@export
enum Foo {
    ...
};

Optionally, the name to be used for the type declaration in the header file
can be different from that used in the .hal interface description by specifying

@export(name="foo_t")
enum Foo {
    ...
};

Finally, overriding the name to be empty, i.e.

@export(name="")
enum Foo {
    ...
};

will cause the generator to emit an anonymous enum.

Bug: 31800672
Change-Id: Idffb2c1700af1c7fd312941d80c3373add8ae558
Test: make
diff --git a/Annotation.h b/Annotation.h
index f2826a0..063b8e4 100644
--- a/Annotation.h
+++ b/Annotation.h
@@ -49,7 +49,7 @@
 
     std::string name() const;
     const AnnotationParamVector &params() const;
-    const AnnotationParam *getParam(const std::string &name);
+    const AnnotationParam *getParam(const std::string &name) const;
 
     void dump(Formatter &out) const;