[IPv6addr] scan address directly into integers in scan_if()
This simplifies the addresss reading code a little by scanning
it directly into 4 32bit unsigned integers which are then converted
into network byte order.

The former construction of scaning the address into 8 strings, each
representing 16bits, and then using sfprintf to write these into
a buffer as integers seems a little bit akward to me.

--HG--
extra : convert_revision : edf64a81bb184478ebf4932ad69b491a14766e3f