Update README to state POSIX.1-2001 as a requirement
@@ -20,7 +20,7 @@ This library is licensed under the Apache License, Version 2.
## From a Tarball
This code is known to work with GCC 4.4+ and clang 3.2+. It should also work
-on other compilers that supports C99, POSIX 2011.11, and the `-fms-extensions
+on other compilers that supports C99, POSIX.1-2001, and the `-fms-extensions
flag` (or equivalent). The latter is needed to allow an anonymous union in a
structure.
