DOMNodeList elements are accessible through array notation

Fixes #67949
Fixed a bug that causes crash when environment variable is access while parsing php.ini
Exposed zend_clean_and_cache_symbol_table() and fixed incorrect efree()
Added info about ext/opcache
Merge branch 'PHP-5.5' into PHP-5.6

* PHP-5.5:
  Added info about ext/opcache
Merge branch 'PHP-5.6'

* PHP-5.6:
  Added info about ext/opcache

Conflicts:
	EXTENSIONS
Fixed bug #68129

Empty usernames and passwords are now treated differently from no username or password

For example, empty password:

    ftp://user:@example.org

Empty username:

    ftp://:password@example.org

Empty username and empty password

    ftp://:@example.org
Updated NEWS for #68129
Merge branch 'PHP-5.5' into PHP-5.6

* PHP-5.5:
  Updated NEWS for #68129
  Fixed bug #68129
Updated NEWS for #68129
Merge branch 'PHP-5.6'

* PHP-5.6:
  Updated NEWS for #68129
  Updated NEWS for #68129
  Fixed bug #68129
Merge branch 'pr/846' into PHP-5.6

* pr/846:
  DOMNodeList elements are accessible through array notation
Updated NEWS for #67949
Merge branch 'PHP-5.6'

Conflicts:
	ext/dom/dom_properties.h
	ext/dom/nodelist.c
	ext/dom/php_dom.c
Copy all the arena allocated data from SHM to process memory at once
Directly use zend_string for php_implode/php_explode

Also drop some unnecessary zval separations and copies
Fix bug #68191: Broken reference across objects
Review a few more SEPARATE_ZVAL_IF_NOT_REF usages
Remove support for classes without class entries

get_class_entry must be non-NULL and return non-NULL.
Remove proxy object implementation