Improve <table> syntax:

Improve <table> syntax:
The <col> element can only appear inside <colgroup>, so use <colgroup>.
The <tbody> element is optional and useless, so don't use it.
Even if we would ever need <thead> or <tfoot>, <tbody> would still be
optional and useless; besides, we will likely never need <thead> or <tfoot>,
simply because our languages don't support such functionality.