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.

The `<signal.h>` header file is part of the standard C89 headers [1] and
on current systems can be included unconditionally.

Since file requires at least C89 or greater, the `HAVE_SIGNAL_H` symbol
defined by Autoconf in Zend.m4 [2] can be ommitted and simplifed.

The bundled libmagic (file) also ommits the usage of HAVE_SIGNAL_H since
5.35 however current version in PHP is very modified 5.34 version and
will be refactored separately. Check for HAVE_SIGNAL_H is therefore
still done in the configure.ac.

Refs:
[1] https://port70.net/~nsz/c/c89/c89-draft.html#4.1.2
[2] https://git.savannah.gnu.org/cgit/autoconf.git/tree/lib/autoconf/headers.m4

* PHP-7.3:
  Fix #77805 phpdbg build fails when readline is shared

* PHP-7.2:
  Fix #77805 phpdbg build fails when readline is shared

The phpdbg sapi module is distributed with the release cycle of PHP.
This patch simplifes phpdbg versioning and bumps it to the PHP_VERSION.

Removed useless filename and lineno arguments, used in DEBUG build.
The patch doesn't break source compatibility of public API (only binary compatibility).