[boost] [config] Type in config/abi_suffix.hpp file

Hi, there is a minor inconsistency I noted in config/abi_suffix.hpp file. This line # error Header boost/config/abi_prefix.hpp must only be used after boost/config/abi_prefix.hpp should be # error Header boost/config/abi_suffix.hpp must only be used after boost/config/abi_prefix.hpp -- Alexei Alexandrov