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/sources/android/native_app_glue/android_native_app_glue.h

@@ -27,7 +27,7 @@
 #include <android/native_activity.h>
 
 #ifdef __cplusplus
-extern "C"
+extern "C" {
 #endif
 
 /**