GDB script improvements (php#17227)

* Support IS_INDIRECT, IS_PTR, IS_ALIAS_PTR when printing zvals
* Pretty print the ce_flags field when pretty printing a zend_class_entry
* Pretty print the const flags when pretty printing a zend_class_constant
* Added a minimal zend_property_info pretty printer to pretty print the flags field
* Added minimal zend_function, zend_op_array, and zend_internal_function pretty printers: The string value is the function/method name, function type (user/internal), and location (when possible). The fn_flags field is pretty printed
* Added a minimal zend_op pretty printer to pretty print the opcode
* Added a zend_refcounted_h pretty printer to pretty print the type_info
* Added minimal pretty printers for zend_object and zend_array
* Print the type and address of pretty-printed structs
* Added gdb commands: print_fn_flags, print_ce_flags, print_prop_flags, print_const_flags, print_ref_type_info, print_opcode, dump_op_array
* Fields of type zend_string, zend_class_entry, zend_array are printed by default in all our pretty printers, using short representation
* Increased the maximum length of printed strings to 200 chars before truncation (was 50)

Author: arnaud-lb