This introduces new stream error handling that allows configurable
handling of stream errors. This can be configured in stream contex.
All streams, ext/standard and ext/phar stream errors are converted to
use the new API.
RFC: https://wiki.php.net/rfc/stream_errors
Closes phpGH-20524

Since GH-20524, _php_stream_open_wrapper_ex() attaches the context to a
stream that has none, including the implicitly substituted default
context. Sharing the default context by reference let a later
stream_context_set_option() on the stream mutate the global default
context, leaking options into every other context-less stream.
Only attach explicitly provided contexts. Stream errors already fall
back to the default context when the stream has none, so error handling
is unaffected.

This introduces new stream error handling that allows configurable
handling of stream errors. This can be configured in stream contex.
All streams, ext/standard and ext/phar stream errors are converted to
use the new API.
RFC: https://wiki.php.net/rfc/stream_errors
Closes phpGH-20524

Since phpGH-20524, _php_stream_open_wrapper_ex() attaches the context to a
stream that has none, including the implicitly substituted default
context. Sharing the default context by reference let a later
stream_context_set_option() on the stream mutate the global default
context, leaking options into every other context-less stream.
Only attach explicitly provided contexts. Stream errors already fall
back to the default context when the stream has none, so error handling
is unaffected.