mod_ssl namespacing: Rename SSL_init_app_data2_idx, SSL_get_app_data2,

and SSL_set_app_data2 from SSL_* to modssl_*. Update references in
README.dsov.* files. Rename static variable SSL_app_data2_idx to just
app_data2_idx since the symbol is internal to ssl_util_ssl.c.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1677143 13f79535-47bb-0310-9956-ffa450edef68