1.0.14.27: rename MAKE-FIXNUM to POINTER-HASH

1.0.14.27: rename MAKE-FIXNUM to POINTER-HASH

 * Use VOP translation instead of %PRIMITIVE.

 * On x86 and x86-64 improve the pointer-hash slightly: use the whole
   address, but none of the tag bits in the hash.

 * Fix type in INDEX-FOR-HASHING: the first argument is a HASH, not an
   INDEX. Given the better quality of low bits on x86oids (and
   hopefully soon on others as well), adjust the mixing a bit.