Changed link from SVG-AAM to Core-AAM

In SVG-AAM 5.4.1 General Rules there is a statement:

    [SVG] user agents MUST conform to the Role Mapping General Rules
    accessibility API computational requirements in [CORE-AAM].

This included a link to the Core-AAM: 
http://www.w3.org/TR/core-aam-1.1/#roleMappingGeneralRules

However, a section with that ID does not exist in the Core-AAM. I 
changed the link to the most likely candidate I could think of, 5.1 
General rules for exposing WAI-ARIA semantics: 
http://www.w3.org/TR/core-aam-1.1/#mapping_general.

I am not absolutely sure I set the target to the right place. But it had 
to be done quickly this evening in order for the TR publication not to 
be delayed. So if I chose the wrong target, I wanted to alert you so you 
can fix it before the next TR publication.

Michael