Travis: only use Apache as web server

Workaround for build errors with PHP built-in web server since
30-Apr-2014 [1].

[1] https://github.com/travis-ci/travis-ci/issues/2235
Provide a description for unknown error types
Separate error type from description with colon

This makes the error message look more like standard PHP errors.
Exit with an error code of 1

This allows the calling script to respond in an appropriate manner in
case an error occurs.
Only exit if error type is configured to HALT

Makes CLI script behave like the web app
Only print message if error type is configured to do so

If display method == DISPLAY_ERROR_NONE, don't print anything.
Don't fall through web-specific error handling

If a non-critical error occurs and we continue code execution as
configured in $g_display_errors, the web-specific handling should not be
executed.
Print backtrace when show_detailed_errors == ON
Add handling for E_DEPRECATED error type