C++ ABI change

GCC 5.x contains libstdc++ with dual ABI support and we have now switched to the new ABI.

While the old C++ ABI is still available, it is recommended that you build all non-repo packages to have the new ABI. This is particularly important if they link to another library built against the new ABI. You can get a list of packages to rebuild using the following shell script:

#!/bin/bash

while read pkg; do
    mapfile -t files < <(pacman -Qlq $pkg | grep -v /$)
    grep -Fq libstdc++.so.6 "${files[@]}" <&- 2>/dev/null && echo $pkg
done < <(pacman -Qmq)

(Original announcement text by Allan McRae [link])