relocatable-prog: Use $ORIGIN trick on more platforms. * m4/relocatable.m4 (gl_RELOCATABLE_BODY): Use $ORIGIN trick also on FreeBSD >= 7.3, DragonFly >= 3.0, NetBSD >= 8.0, OpenBSD >= 5.4, Solaris >= 10, Haiku. But don't use it on Android. * build-aux/reloc-ldflags: Allow the use of the $ORIGIN trick also on Hurd, FreeBSD, DragonFly, NetBSD, OpenBSD, Solaris, Haiku.