out of libmysql into separate dynamic plugins in the plugin/ directory.
move dialog and auth_socket plugins out of the plugin directory with examples into
dedicated directories in plugin/
when checking the ABI with the C Preprocessor. Also, add the
new hearders to the cmake based ABI check.
cmake/abi_check.cmake:
Add headers which were added to the autotools ABI check.
Remove trailing spaces.
include/mysql/client_plugin.h:
Guard the inclusion of system headers.
