installing gtk1.2 and glib1.2.10, what is "install-prefix"

[philip dahlquist <dahlquist kreative net>]

ok, i'm installing the aforementioned libraries using the following
instructions:

Simple install procedure
========================

  % gzip -cd gtk+-1.2.10.tar.gz | tar xvf - # unpack the sources
  % cd gtk+-1.2.10                         # change to the toplevel directory
  % ./configure                            # run the `configure' script
  % make                                   # build GTK

  [ Become root if necessary ]
  % rm -rf /install-prefix/include/gtk /install-prefix/include/gdk
  % make install                           # install GTK


what is the "install-prefix" directory.  there are quite a few
candidates for this label. is it the source directory gtk+-1.2.10, or
/usr/include/gtk1.2, or /usr/local, or what?

i did a search for "glib.h", and it came up with several options, namely /usr/include/glib1.2/glib.h,
so i renamed them just in case i needed them because i picked the wrong glib.h.

thanks,
philip