Do `chmod -R a+r *' before building the tar files,

Estimated hours taken: 0.1

Mmakefile:
	Do `chmod -R a+r *' before building the tar files,
	to ensure that all the files in them are readable by everyone.

Mmakefile

@@ -224,6 +224,7 @@ tar: README INSTALL
 	-rm -f config.status config.cache config.log configure.log
 	-rm -f runtime/mercury_conf.h boehm_gc/mercury_boehm_gc_conf.h
 	-rm -f Mmake.common
+	chmod -R a+r *
 	# Package up the mercury directory with some subdirectories
 	# excluded, into a gzipped tar archive that will unpack into
 	# mercury-compiler-$(VERSION).