C Headers for threading support on GCC, Raspbian?

I want to compile a very program for my Raspberry Pi that uses the thrd_sleep() function as defined in header file in the c11 standard library. I want to use the C11 library for cross-platform compatibility.

A google search I previously did led me to believe that updating gcc should update the available headers because it did not mention any other commands. I did not change the package source for various reasons. I have installed the newest available versions of gcc: gcc-4,6, gcc-4.7, and gcc-4.8. I have tried all of the commands:

gcc main.cgcc-4.6 main.cgcc-4.7 main.cgcc-4.8 main.c

and I get the same error every time:

main.c:2:21: fatal error: threads.h: No such file or directory

It is now evident that I need to install something else. My other searches have failed to conclude anything.

1. What package includes the C11 headers

2. Do I have to link any libraries to include the C11 thread support features?