#2 switch build system from imake to autotools

[Barak A. Pearlmutter]

I've done some major surgery: ripped out the imake/ivmake based build system in its entirety and replaced it with autoconf/automake, aka, GNU autotools. These are tested to work under Debian, but would need tweaking and in particular integration of the generated config.h into the C++ sources to be properly portable. Changes available in branch "autotools" of git repository github.com/barak/ivtools