Recommended version of SWIG for building mapscript

[Howard Butler]

>I'll let Assefa comment on the version of SWIG used for MS4W.

Jeff or Assefa would have to absolutely confirm, but I believe the 
Buildkit (and therefore MS4W) is using 1.2.27 for the 4.8 series.  I 
made some patches (icky #ifdef checks) to allow 1.3.29 to work (SWIG 
renamed some things between versions).

In my experience, 1.3.29 has been pretty stable, and the swig folks 
haven't ripped off another quick release like they are apt to do if 
something is wrong with it.

I would also note that both the osx and linux build slaves on the 
buildbot are using 1.3.29.

Howard