Remove c++11 workaround for older versions of GCC. Now gives an error for releases older than 4.7
Remove old workaround for bug in GCC 4.3.1-2
Removed workaround for GCC bug in 4.5.1-2
This duplicate line was added in r6644. I don't see why it's there.
Check for Boost header include directory separately since that's what we are actually interested in. Moved Wold-style-cast to list of extra warnings. Don't add the empty variable to Release builds
Checks that GCC is at least version 4.7 which is required to build. Removed various workarounds for older GCC-versions