New features: external input file and forced sending address

In 2004-06-28 sipp snapshot
(http://sipp.sourceforge.net/snapshots/sipp.2004-06-28.tar.gz), 2 new
features and one bug fix have been added:

1/ Input file feature (contributed by Shriram - thanks!!! - and enhanced
by Joseph). Now you can use "-inf file_name" as a command line parameter
to input values into the scenarios. The first line of the file should
say whether the data is to be read in sequence (SEQUENTIAL) or random
(RANDOM) order. Each line corresponds to one call and has one or more
';' delimited data fields and they can be referred as field0 etc in the
xml scenario file.
Example:
SEQUENTIAL
Sarah;32.125.47.98
Bob;12.45.67.89

Will be read in sequence (first call will use first line, second call
second line).
At any place where the keyword "[field0]" appears in the scenario file,
it will be replaced by either "Sarah" or "Bob" depending on the call.
At any place where the keyword "[field1]" appears in the scenario file,
it will be replaced by either "32.125.47.98" or "12.45.67.89" depending
on the call.
At the end of the file, sipp will re-start from the beginning.
The file is not limited in size.

Think of the possibilities of this feature. They are huge.

2/ Remote sending address. Until now, sipp was always responding using
the same IP socket when it received a message in server mode. This
caused some problems to test proxies for example (reported by Tarek
Rogers). There is a new option in the command line, "-rsa host:port",
which allows you to force the "Remote Sending Address".

3/ Bug fix: there was a bug when parsing the "To:" header which was
parsed beyond the header limit.