[developers] compiling latest revisions of PET (without XML support)

[Stephan Oepen]

hei!

call me old-fashioned, but i still compile my PET with `--disable-xml'
(lacking all the right libraries on my laptop).  in recent revisions,
that appears to no longer be possible.

ben, could i get you to wrap a few more #ifdef-s around your code? 

                                       many thanks in advance  -  oe
                                                   
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+++ Universitetet i Oslo (IFI); Boks 1080 Blindern; 0316 Oslo; (+47) 2285 7989
+++     CSLI Stanford; Ventura Hall; Stanford, CA 94305; (+1 650) 723 0515
+++       --- oe at csli.stanford.edu; oe at ifi.uio.no; stephan at oepen.net ---
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