Changeset 45611

Coding Standards: Fix instances of WordPress.PHP.NoSilencedErrors.Discouraged.

Noteable changes:

• The magic_quotes_runtime and magic_quotes_sybase settings were removed in PHP 5.4, so no longer need to be set.
• Some functions that use external libraries can generate errors that can't be tested for, so are globally allowed to silence errors.
• Quite a few functions would cause errors if safe_mode was set. This setting was removed in PHP 5.4.
• Only a handful of header() calls needed corresponding headers_sent() checks for unit tests to pass, but more may need to be added as the nightlies builds are tested.

See #46732.