NDK: Last cleanup of the platform headers

- fix a declaration omission in 3/<grp.h>
- add missing 8/<err.h>
- simplify 8/<stdio.h>
- update 9/ headers to the latest Bionic versions
- fix a typo in android_native_app_glue.h
- use __BEGIN_DECLS .. __END_DECLS whenever possible.
- remove C++-style comments from headers

Change-Id: I58b98b3973cde494436206194ba33416a11ca8ee

ndk/platforms/android-9/include/android/configuration.h

@@ -19,9 +19,7 @@
 
 #include <android/asset_manager.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
+__BEGIN_DECLS
 
 struct AConfiguration;
 typedef struct AConfiguration AConfiguration;
@@ -312,8 +310,6 @@ int32_t AConfiguration_match(AConfiguration* base, AConfiguration* requested);
 int32_t AConfiguration_isBetterThan(AConfiguration* base, AConfiguration* test,
         AConfiguration* requested);
 
-#ifdef __cplusplus
-};
-#endif
+__END_DECLS
 
-#endif // ANDROID_CONFIGURATION_H
+#endif /* ANDROID_CONFIGURATION_H */