Build warnings

[dirkschulze]

A fresh build gives following build warnings:

conform.html:354:68: warning: ambiguous name "href" matching multiple attributes
struct.html:653:36: warning: ambiguous name "href" matching multiple attributes
linking.html:151:54: warning: ambiguous name "href" matching multiple attributes
linking.html:286:21: warning: ambiguous name "href" matching multiple attributes
linking.html:300:31: warning: ambiguous name "href" matching multiple attributes
linking.html:301:23: warning: ambiguous name "href" matching multiple attributes
linking.html:376:20: warning: ambiguous name "href" matching multiple attributes
linking.html:453:12: warning: ambiguous name "href" matching multiple attributes
linking.html:476:30: warning: ambiguous name "href" matching multiple attributes
linking.html:568:39: warning: ambiguous name "href" matching multiple attributes

[AmeliaBR]

Well, for the life of me I can't figure out what changed to have these warnings show up now and not on previous builds, but the issue is that these are references to a generic href attribute without an element context, and definitions.xml only defines href attributes for specific elements (because they usually have element-specific definitions about what they do).