remove one more redundant decode of the extensions present bit.

 remove one more redundant decode of the extensions present bit.

change the decode of sequence and extensions  to assume the lower bound for the number of extensions is 1 and thus 1 have to be added to the encoded value.

dont know if this is right or not, the satndard x691 does not mention anything
about the lb being 1 and the value being semiconstrained but a note at 18.8
does mention that the number of extensions can not be 0.

i think there is a difference between saying a value can not be zero and
between saying the lower bound is 1.  but hey it is a telco standard.

the change might be right or it might be wrong.
i think it is wrong or else the standard is wrong.
it at least dissects the very few captures i have properly.
telco guys, either give feedback or live with the dissector being potentially
wrong.
its that easy.

svn path=/trunk/; revision=7990