[sv-cc] Modifications to 1456 and 1488

Instead of dealing with the effect of C setjmp/longjmp on DPI context as
a separate issue,

I've added a short amount of text to the 2 existing Mantis items to
address the issue:

 

. in 1456 for C-specific sections on context in Annex F,

. in 1488 for the general section on DPI context (26.4.3).

 

Ralph