cpoll: added UNIXException and FileNotFoundException classes
cppsp: improved error handling

* CP::FileNotFoundException is now thrown by cppspManager::loadPage()
when a file can not be found, instead of returning NULL
* CP::FileNotFoundException is automatically translated into an HTTP 404
by the default error handler
* when a FileNotFoundException occurs, the exact path that was not found
is displayed for easier debugging
cppsp: SSI (server-side include) support

note: SSI is only supported for dynamic pages
cppsp: added "debug mode" where temporary .so and .C files would not be deleted
cppsp: dir_list.cppsm: redirect if there is no trailing "/" when visiting a directory
package_cppsp: added run_cppsp and cppsp_clean scripts
cppsp: added indexpage.cppsm which allows visits to directories to be treated as visits to index.cppsp or index.html within