is a fixnum and added meta-asserts to verify that it is in a couple of
others, to facilitate future changes to vector typing. vectors are
now treated essentially like fxvectors, strings, and bytevectors.
cmacros.ss, cpnanopass.ss, prims.ss, mkheader.ss,
alloc.c, gc.c, scheme.c
original commit: 564542d32bbae6b33cef808613238d5a4a2a8ee2