ndk: <sys/cdefs.h> minor update

This patch fixes some formatting issues in <sys/cdefs.h>:

- change '#if __STDC_VERSION__ > xxx' into '#if defined(__STDC_VERSION__) && __STDC_VERSION > xxx'
- add __LIBC_HIDDEN__ definition (not technically required, but makes comparing the headers with upstream easier)

Change-Id: I5fd13224181e2f757fb01cb99c93508c3a6d9e13
2 files changed