ITS#7173 Fixing prototype of function in manpage to match prototype in C header.

    The prototype for ldap_modify_ext() in the C header file declares
    msgidp as "int *", however the current manpage declares msgidp as
    "int **". This patch updates the manpage to accurately reflect the
    C header.

Signed-off-by: David M. Syzdek <syzdek@bindlebinaries.com>