Add a `zend.exception_string_param_max_len` ini setting.
(same suffix as `log_errors_max_len`)

Allow values between 0 and 1000000 bytes.
For example, with zend.exception_string_param_max_len=0,
"" would represent the empty string, and "..." would represent something
longer than the empty string.
Previously, this was hardcoded as exactly 15 bytes.

Discussion: https://externals.io/message/110717

Closes GH-5769

[ci skip]

Some extension may need to retrieve the `gdImagePtr` from an `GdImage`
object; thus, we export the respective function.  To not being forced
to include gd.h in php_gd.h, we use the opaque `struct gdImageStruct *`
as return type.

We also rename php_gd2.dll to php_gd.dll, since there's not really much
point in giving the DLL a version number, since there is no php_gd.dll
for years (if there ever has been).  Renaming, on the other hand,
matches the name on other systems (gd.so), and allows to actually use
`ADD_EXTENSION_DEP()`.

According to <https://wiki.php.net/rfc/unbundle_xmlprc> we unbundle
ext/xmlrpc.

If opcache.record_warnings is enabled, opcache will record
compilation warnings and replay them when the file is included
again. The primary use case I have in mind for this is automated
testing of the opcache file cache.

This resolves bug #76535.

* PHP-7.4:
  Clarify session.cookie_samesite="None"

* PHP-7.3:
  Clarify session.cookie_samesite="None"

* PHP-7.4:
  Fix typo in php.ini comment

* PHP-7.3:
  Fix typo in php.ini comment