Type tags in NodeFlags could be compressed

Type tags in NodeFlags could be compressed
https://bugs.webkit.org/show_bug.cgi?id=79299

Because existing node flags which indicate the class of each node
are mutually exclusive, these flags can be represented as a enum.
This patch introduces Node::NodeTypeTag to turn these flags into a
enum, and embeds it into Node::m_nodeFlags.

Reviewed by Antti Koivisto.

No new tests. No bahavior change.

* dom/Node.cpp:
(WebCore):
* dom/Node.h:
(WebCore):
(Node):
(WebCore::Node::typeTag):
(WebCore::Node::parentNode):
(WebCore::Node::parentNodeGuaranteedHostFree):
(WebCore::Node::isContainerNode):
(WebCore::Node::isElementNode):
(WebCore::Node::isStyledElement):
(WebCore::Node::isTextNode):
(WebCore::Node::isHTMLElement):
(WebCore::Node::isSVGElement):
(WebCore::Node::isShadowRoot):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@114333 268f45cc-cd09-0410-ab3c-d52691b4dbfc