[except.handle] Add a missing ", or" after penultimate bullet.

Fixes #344.

Author: zygoloid

source/exceptions.tex

@@ -538,7 +538,7 @@
 a standard pointer conversion~(\ref{conv.ptr}) not involving conversions
 to pointers to private or protected or ambiguous classes
 \item%
-a qualification conversion
+a qualification conversion, or
 
 \end{itemize}