Log Message:
Various updates to smlnj so it builds on NetBSD/powerpc again:
 * Modernize the powerpc entry in signal-sysdep.h to use the
   various _UC_MACHINE_ macros.
 * mk.ppc-netbsd: don't pass an empty RANLIB variable, causing build failure.

Also make checksums of all the three arch-specific distfiles ("boxes"),
for sparc, x86 and ppc.

Bump PKGREVISION.