d81e4bdd Implement malloc_vsnprintf().

[Mike Hommey]

Hi,

This commit added a use of __thread in malloc_vtprintf. Unfortunately,
this keyword is not supported everywhere, and this breaks building on
OSX, where the keyword is not supported by the compiler.

It also breaks assumptions you'd make when you --disable-tls, which is
needed on Android, because while the compiler supports __thread, the
runtime doesn't.

Cheers,

Mike