Move extern declarations to headers.

include/ldap_features.h.nt

include/portable.h.nt

libraries/libldap/disptmpl.c

libraries/libldap/dsparse.c

libraries/libldap/error.c

libraries/libldap/getfilter.c

libraries/libldap/kbind.c

libraries/libldap/ldap-int.h

libraries/libldap/srchpref.c

libraries/libldap/ufn.c