[Maxima] Documentation files contents.hhc index.hhk header.hhp maxima.hhp

[David Billinghurst]

I have made some recent changes to "improve" the windows build process. See
http://www.math.utexas.edu/pipermail/maxima/2012/028800.html for motivation

For all platforms, we install the files contents.hhc index.hhk header.hhp
and maxima.hhp from doc/info/*.  As far as I can tell:
  - these are only used on windows to build the maxima.chm file
  - following my recent changes, we don't need to install them

I propose not installing these files and will make the changes if there are
no complaints.

     D