The php_stream_read() and php_stream_write() functions now return
an ssize_t value, with negative results indicating failure. Functions
like fread() and fwrite() will return false in that case.

As a special case, EWOULDBLOCK and EAGAIN on non-blocking streams
should not be regarded as error conditions, and be reported as
successful zero-length reads/writes instead. The handling of EINTR
remains unclear and is internally inconsistent (e.g. some code-paths
will automatically retry on EINTR, while some won't).

I'm landing this now to make sure the stream wrapper ops API changes
make it into 7.4 -- however, if the user-facing changes turn out to
be problematic we have the option of clamping negative returns to
zero in php_stream_read() and php_stream_write() to restore the
old behavior in a relatively non-intrusive manner.

RFC: https://wiki.php.net/rfc/tostring_exceptions

And convert some object to string conversion related recoverable
fatal errors into Error exceptions.

Improve exception safety of internal code performing string
conversions.

Autoconf defines PACKAGE_* symbols:
- PACKAGE_NAME
- PACKAGE_VERSION
- PACKAGE_TARNAME
- PACKAGE_STRING
- PACKAGE_BUGREPORT
- PACKAGE_URL

and appends them to the generated config.h.in files. With AC_INIT change
via afd52f9d9986d92dd0c63832a07ab1a16bf11d53 where package version, URL,
bug report location and similar meta data are defined, these
preprocessor macros are then non empty strings in the generated
configuration header file. When using phpize, PHP shares the config
files in extensions, warnings of redefined macros appear, such as:
- `warning: 'PACKAGE_NAME' macro redefined`

This patch now disables these non utilized symbols in the generated
config header files.

Better practice would be to include only API specific headers where
needed but this would require even more refactorings. Some extensions
such as pcre, pgsql, and pdo_pgsql solve this issue by undefining some
of these symbols before including the library configuration headers in
the code also. Because these symbols can be defined by any library which
uses Autotools.

Additionally, the unused PACKAGE_* symbols were cleaned for the bundled
libmbfl library and with this patch not needed undef code removed.

This is unnecessary convoluted... we just want to find the position
of the dot. Using php_strtok_r requires a copy of the string, and the
implementation also relied on the specific semantics of the scratch
space that strtok_r uses.

When a connection is closed, we also need to remove the hash entry
from the regular_list, as it now points to freed memory. To do this
store a reverse mapping from the connection to the hash string.

It would be nicer to introduce a wrapping structure for the pgsql
link resource that could store the hash (and notices), but that would
require large changes to the extension, so I'm going for a more
minimal fix here.