chan_sip: Send real CallerID information with P-Assserted-Identity (RFC-3325)

Prior too this patch, the P-Asserted-Identity header would include anonymous
caller id information which seems to go against the point of the
P-Asserted-Identity header. Now the real caller ID information will be
included in this header. Also, no privacy header would be included.
This patch adds 'Privacy: id' to outgoing SIP messages that include the
P-Asserted-Identity header.

(closes issue AST-1301)
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Merged revisions 411189 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/11@411190 f38db490-d61c-443f-a65b-d21fe96a405b