This GNU extension doesn't work for me on Mac OS X 10.8 (Mount Lion) and also not on Windows 7 using the same example from the StackOverflow link. It's documented in the GNU libc documentation. I imagine it only works on GNU compiled libc. Haven't checked on Linux yet.
But I will include recognition of the optional ' (tick) anyway in the next version. So it may work on some platforms.
PS: does work on UBUNTU Linux!