Makefile: Eliminate the "make install-emacs" target.

Makefile: Eliminate the "make install-emacs" target.

Instead, simply byte-compile the emacs source files as part of "make"
and install them as part of "make install". The byte compilation is
made conditional on the configure script finding the emacs binary.
That way, "make; make install" will still work for someone that doesn't
have emacs installed, (which was the only reason we had made a separate
"make install-emacs" target in the first place).