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

It also adds pthread_atfork() for API level 11 (3.0)

Change-Id: Ie814208335ed102d4c178a4c373e6963e5dcc9dd
5 files changed