Merge mainstream 'master' branch into refactoring

Merge mainstream 'master' branch into refactoring
During merge I had to revert:
	Nikita's patch for php_splice() (it probably needs to be applyed again)
	Bob Weinand's patches related to constant expression handling (we need to review them carefully)
	I also reverted all our attempts to support sapi/phpdbg (we didn't test it anyway)

Conflicts:
	Zend/zend.h
	Zend/zend_API.c
	Zend/zend_ast.c
	Zend/zend_compile.c
	Zend/zend_compile.h
	Zend/zend_constants.c
	Zend/zend_exceptions.c
	Zend/zend_execute.c
	Zend/zend_execute.h
	Zend/zend_execute_API.c
	Zend/zend_hash.c
	Zend/zend_highlight.c
	Zend/zend_language_parser.y
	Zend/zend_language_scanner.c
	Zend/zend_language_scanner_defs.h
	Zend/zend_variables.c
	Zend/zend_vm_def.h
	Zend/zend_vm_execute.h
	ext/date/php_date.c
	ext/dom/documenttype.c
	ext/hash/hash.c
	ext/iconv/iconv.c
	ext/mbstring/tests/zend_multibyte-10.phpt
	ext/mbstring/tests/zend_multibyte-11.phpt
	ext/mbstring/tests/zend_multibyte-12.phpt
	ext/mysql/php_mysql.c
	ext/mysqli/mysqli.c
	ext/mysqlnd/mysqlnd_reverse_api.c
	ext/mysqlnd/php_mysqlnd.c
	ext/opcache/ZendAccelerator.c
	ext/opcache/zend_accelerator_util_funcs.c
	ext/opcache/zend_persist.c
	ext/opcache/zend_persist_calc.c
	ext/pcre/php_pcre.c
	ext/pdo/pdo_dbh.c
	ext/pdo/pdo_stmt.c
	ext/pdo_pgsql/pgsql_driver.c
	ext/pgsql/pgsql.c
	ext/reflection/php_reflection.c
	ext/session/session.c
	ext/spl/spl_array.c
	ext/spl/spl_observer.c
	ext/standard/array.c
	ext/standard/basic_functions.c
	ext/standard/html.c
	ext/standard/mail.c
	ext/standard/php_array.h
	ext/standard/proc_open.c
	ext/standard/streamsfuncs.c
	ext/standard/user_filters.c
	ext/standard/var_unserializer.c
	ext/standard/var_unserializer.re
	main/php_variables.c
	sapi/phpdbg/phpdbg.c
	sapi/phpdbg/phpdbg_bp.c
	sapi/phpdbg/phpdbg_frame.c
	sapi/phpdbg/phpdbg_help.c
	sapi/phpdbg/phpdbg_list.c
	sapi/phpdbg/phpdbg_print.c
	sapi/phpdbg/phpdbg_prompt.c