Allows to load PITR and Map-resolvers from fqdns

This patch adds 2 functions in lisp_lib.c:
-lispd_get_address5 ( 5 because it accepts 5 arguments) that converts an address either from an IP or an hostname string. Once it has convert the hostname into a list of sockaddr, iterate over these sockaddr and passes them to the function passed as a callback.
-copy_addr_from_sockaddr which is self explanatory

This should not add any maintenance overhead once it replaces older lispmob functions such as those relying on gethostname2 since the man says anyway that gethostname* functions are depreciated in favor of getaddrinfo, which lispd_get_address5 uses.

Here is an output of config loading.
DEBUG: Configuration file: RLOC probing not defined. Setting default values: RLOC Probing Interval: 30 sec.
DEBUG: converted addr_str [intouch-ams-mr-ms-1.rloc.lisp4.net] to address [217.8.98.42]
DEBUG: Added intouch-ams-mr-ms-1.rloc.lisp4.net to map-resolver list
DEBUG: converted addr_str [tdc-mr-ms.rloc.lisp4.net] to address [193.162.145.50]
DEBUG: Added tdc-mr-ms.rloc.lisp4.net to map-resolver list
DEBUG: Added 193.162.145.46 to proxy-etr list
DEBUG: converted addr_str [eqx-ash-pxtr.rloc.lisp4.net] to address [69.31.31.98]
DEBUG: Added eqx-ash-pxtr.rloc.lisp4.net to proxy-itr list