* don't clobber CPPFLAGS, LIBS, and the like

* replace drand48() calls by rand()
  - former does not exist on mac osx


* PR from Christina Rossmanith <cr@neuro.ma.uni-heidelberg.de>

    I'm trying to compile bicpl as a prerequisite for
    register+Display. I've installed the most recent version of netpbm
    which is 10.8. Since the release of version 10 there is no libppm
    but libnetpbm instead. Thus configure sh ould check for either the
    three libs or for the new lib.  I've no experience with configure
    stuff so I just report the problem without supplying a general
    solution. I've modified my configure.


* build with SGI image library should be an option
  - MNI's /usr/local should be built with SGI image lib

* PPM code should check that it really gets a valid PPM
  file on read



