C++ 11/14

[kevina]

The next major version of Aspell, 0.62, is likely to require C++11 support and use select features from C++14.

The minimum support compilers is likely to be Gcc 4.9 and Clang 3.4. Gcc 4.9 is the default for Debian Jessie, and Clang 3.4 is available for Ubuntu 12.04, so I am not anticipating this to create any problems.