[whatwg] A few spec typos

[Michael A. Puls II]

section 1.3 under Authoring tools and markup generators:
"However, since an authoring tools is likely unable to determine the
difference, an authoring tool is exempt from that requirement."

"Since an authoring tools is" -> "since an authoring tool is" or
"since authoring tools are"

Section 1.3.1:
"Unless other specified, if a DOM attribute that is a signed numberic
type is assigned a negative value, a NOT_SUPPORTED_ERR exception must
be raised."

1. "Unless other specified" sounds funny to me. I get what it's
saying, but maybe it could be worded differently. Was "otherwise"
intended in that case?

2. Instead of "signed numberic", should that be "unsigned numeric"?

1.4 terminology
In "The term root element..." part:

"or the node itself is there is none" -> "or the node itself if there is none"

-- 
Michael