1.0.5.14: make PURIFY a no-op on gencgc

1.0.5.14: make PURIFY a no-op on gencgc

         * Purification doesn't really make any sense with gencgc, since we
           have an uncollected generation with a write barrier these days.
         * Apparently it had also bitrotted on ppc/gencgc between 1.0.0 and
           1.0.4, causing crashes with software doing (SAVE-LISP-AND-DIE
           ... :PURIFY T), for example Maxima. (Reported by Rex Dieter)
         * So make PURIFY a no-op on gencgc, and remove about 600 lines worth of
           #ifdeffed OAOO violations from purify.c.
         * Allows shrinking the static and read-only spaces into something
           sensible (arbitrary value of 1MB selected), and moving all of them
           closer together to reduce the virtual address space footprint.
         * Move + shrink the linkage-table while we're at it.