ndk: <pthread.h>: formatting + updates

This patch improves the formatting of <pthread.h> as exposed by the NDK:

- change '#if __cplusplus' into '#ifdef __cplusplus'
- change C++-style comment into C-style comment

Change-Id: Ib093058e8d7a7554d8329a40e102cde11d065932

ndk/platforms/android-3/include/pthread.h

@@ -103,7 +103,7 @@ typedef volatile int  pthread_once_t;
 /*
  * Prototypes
  */
-#if __cplusplus
+#ifdef __cplusplus
 extern "C" {
 #endif
 
@@ -231,7 +231,7 @@ extern void  __pthread_cleanup_pop(__pthread_cleanup_t*  c,
         __pthread_cleanup_pop( &__cleanup, (execute)); \
     } while (0);
 
-#if __cplusplus
+#ifdef __cplusplus
 } /* extern "C" */
 #endif
 
@@ -240,4 +240,4 @@ extern void  __pthread_cleanup_pop(__pthread_cleanup_t*  c,
 #define LONG_LONG_MAX __LONG_LONG_MAX__
 #define LONG_LONG_MIN (-__LONG_LONG_MAX__ - 1)
 
-#endif // _PTHREAD_H_
+#endif /* _PTHREAD_H_ */