[TYPO3-project-4-3] improve the errorhandling

[Rupert Germann]

hi & rfc

here's a new approach to make the errorhandling fit for final.

features:
- if display of errors is enabled and an error occurs this error is 
displayed as flashmessage
- BE error flashmessages are displayed by template.php
- FE error flashmessages are displayed in the adminpanel (see screenshot)
- to distinguish between production- and debug-mode I introduced a new 
constant ERRORHANDLER_MODE which depends on the configured exceptionhandler
- all calls to errorhandling or exceptionhandling are logged to syslog
to enable the syslog, add this to your localconf.php:
$TYPO3_CONF_VARS['SYS']['systemLog'] = 'error_log,,2';	
$TYPO3_CONF_VARS['SYS']['systemLogLevel'] = 0;

- I introduced a new TYPO3_CONF_VARS parameter:
$TYPO3_CONF_VARS['SYS']['errorHandlerErrors']

this parameter configures which errors reach the errorhandler.

$TYPO3_CONF_VARS['SYS']['exceptionalErrors'] is still used, it 
configures the errors which should be converted to an exception.

So we have 2 kind of errors: errorhandler errors and exceptionsl errors.

The default configuration looks like this:

'errorHandlerErrors'=> E_ALL ^ E_NOTICE,
'exceptionalErrors' => E_ALL ^ E_NOTICE ^ E_WARNING ^ E_USER_ERROR ^ 
E_USER_NOTICE ^ E_USER_WARNING

That means: everything but E_NOTICE reaches the errorhandler. But the 
errorhandler function throws only an exception on exceptional errors 
like e.g. E_RECOVERABLE_ERROR.


INFO:
this patch contains patch 12130 v5.


greets
rupert