Support for _POSIX_THREAD_SAFE_FUNCTIONS

[krnekit]

Though some (or may be all?) posix thread-safe functions is available in Bionic, the toolchain always undefine _POSIX_THREAD_SAFE_FUNCTIONS. Because of this, software cannot rely, that thread-safe functions available and must use not-safe alternatives, which causes bugs.

Can you enable this define?

[DanAlbert]

Looks like bionic itself (in the platform, not in the NDK) actually does have this fixed. @jmgao is working on syncing the current headers with the NDK (I'm guessing we're going to have to be careful about when this is enabled, as not all platforms have those functions).