Using this requires care! The zpp implementation for this union
must be consistent with the arginfo implementation!
Apart from array|object, this is probably only the case for
int|float right now.
Fix the string generated when the `ns\class` is passed to a macro
#define ESCAPE(x) #x
// puts(ESCAPE(ns\class)); // warning: unknown escape sequence: \c
puts(ESCAPE(ns\\class)); // Properly prints ns\class to stdout.
Signature stubs for internal functions are specified in xyz.stub.php,
from which we generate actual arginfo structures in xyz_arginfo.h.
This file then needs to be included in the implementation appropriately.
Arginfo from stubs can be regenerated using scripts/dev/gen_stub.php.
However, this should also automatically happen when the stub file is
modified.
