Implemented Traits for PHP as proposed in the RFC [TRAITS]

Implemented Traits for PHP as proposed in the RFC [TRAITS]

# RFC http://wiki.php.net/rfc/horizontalreuse#traits_-_reuse_of_behavior
# Ok, here we go, I guess that will result in more discussion, which is fine
# by me. But now, the patch is here, and properly archived.
#
# See below a list of notes to the patch, it also includes a list of
# points which should be fixed
#
# Internals of the Traits Patch
# -----------------------------
#
# Open TODOs
# """"""""""
#
# - Reflection API
# - support for traits for internal classes
#   - currently destroy_zend_class does not handle that case
#
# Introduced Structures
# """""""""""""""""""""
#
# Data structures to encode the composition information specified in the
# source:
#  - zend_trait_method_reference
#  - zend_trait_precedence
#  - zend_trait_alias
#
# Changes
# """""""
#
# zend_class_entry
#  - uses NULL terminated lists of pointers for
#    - trait_aliases
#    - trait_precedences
#    - do you prefer an explicit counter?
#    - the information is only necessary during class composition
#      but might be interesting for reflection
#    - did not want to blow up class further with not really necessary length counters
#
# added keywords
#   - trait
#   - insteadof
#
# Added opcodes
#  ZEND_ADD_TRAIT
#    - similar to ZEND_ADD_INTERFACE
#    - adds the trait to the list of traits of a class, no actual composition done
#  ZEND_BIND_TRAITS
#    - emitted in zend_do_end_class_declaration
#    - concludes the class definition and will initiate the trait composition
#      when the class definition is encountered during runtime
#
# Added Flags
#   ZEND_ACC_TRAIT = 0x120
#   ZEND_ACC_IMPLEMENT_TRAITS = 0x400000
#   ZEND_FETCH_CLASS_TRAIT = 14
#
# zend_vm_execute.h
#  - not sure whether the handler initialization (ZEND_ADD_TRAIT_SPEC_HANDLER,
#    ZEND_BIND_TRAITS_SPEC_HANDLER) is correct, maybe it should be more selective
#
# zend_compile.c
#  - refactored do_inherit_method_check
#    split into do_inherit_method_check and do_inheritance_check_on_method
#  - added helper functions use a '_' as prefix and are not mentioned in the
#    headers
#  - _copy_functions
#    prepare hash-maps of functions which should be merged into a class
#    here the aliases are handled
#  - _merge_functions
#    builds a hash-table of the methods which need to be added to a class
#    does the conflict detection
#  - reused php_runkit_function_copy_ctor
#    - it is not identical with the original code anymore, needed to update it
#      think I fixed some bugs, not sure whether all have been reported back to runkit
#    - has to be renamed, left the name for the moment, to make its origin obvious
#    - here might be optimization potential
#    - not sure whether everything needs to be copied
#      - copying the literals might be broken
#        - added it since the literals array is freed by efree and gave problems
#          with doubled frees
#      - all immutable parts of the zend_op array should not be copied
#        - am not sure which parts are immutable
#        - and not sure how to avoid doubled frees on the same arrays on shutdown
#  - _merge_functions_to_class
#    does the final merging with the target class to handle inherited
#    and overridden methods
#  - small helper for NULL terminated lists
#    zend_init_list, zend_add_to_list
#
# zend_language_parser.y
#  - reused class definition for traits
#    - there should be something with regard to properties
#      - if they get explicitly defined, it might be worthwhile to
#        check that there are no collisions with other traits in a composition
#        (however, I would not introduce elaborate language features to control that
#         but a notice for such conflicts might be nice to the developers)