while here also delete the two remaining makefiles from before the -portable merge.

I'm not proud of that hack, which is a double hack in fact, but I've already wasted too much time on this. The first hack is the PATH mangling, and the second the $$(cd ... ; pwd) to obtain an *absolute* path: for build in-tree top_builddir is just `.' which isn't really helpful after a cd.

Trying to maintain two branches was impossible at this stage for me alone, so I'll recognize my stupidity and merge the portable branch into the main one. The repository will build using autotools.