documentation errors for table files

Mike Corcoran spotted a couple of minor problems. The ogip_92_009 memo refers to the incorrect location for the wftbmd.f and .c files. It should be $HEADAS/../ftools/spectral/tables/. Also the onepar and twopar Makefile don't work because they need to refer to the correct version numbers of xanlib and cfitsio - I fixed this by switching to standard HEADAS Makefiles so running hmake will automatically pick up current versions of libraries. These changes are checked in but won't make the imminent HEAsoft 6.5 release.