family has a set of debug commands that allow you to log the traffic on a
WAN or dialup connection as text, e.g.

RECV-iguana:241:(task: B04E12C0, time: 1975358.50) 15 octets @ 8003D634
  [0000]: FF 03 00 3D C0 06 C9 96 2D 04 C1 72 00 05 B8

Created wtap_seek_read() which parses the textual data for and Ascend
trace, and does a normal fseek() and fread() for any other file type.
The fseek()/fread() pairs in file.c were replaced with the new function.

svn path=/trunk/; revision=652