* Makefile.in (enable_grub_emu): New variable.
* configure.ac (--enable-grub-emu): New option.
Do the checks for (n)curses only if `--enable-grub-emu' is requested.
* conf/i386-efi.rmk (sbin_UTILITIES): Add `grub-emu' only if requested.
* conf/i386-pc.rmk: Likewise.
* conf/powerpc-ieee1275.rmk: Likewise.
* conf/sparc64-ieee1275.rmk (bin_UTILITIES): Likewise.
