Linux 3.13 compatibility for older GCC versions

This enables Linux 3.13 compatibility without depending on newer versions of GCC. It supersedes pull request #2135. It has been subject to tests on CentOS 6.5 with Linux 3.13.6 and GCC 4.4.7-4; Gentoo with Linux 3.13.0 and GCC 4.7.3-r1; and Gentoo with Linux 3.12.6 and GCC 4.8.2-r1. These tests detected no regressions. The CentOS test confirmed that this enables compatibility with older GCC versions. However, that should be self-evident when reading the commit messages.