fix a couple of leaks

fix a couple of leaks

* libguile/bytevectors.h:
* libguile/bytevectors.c (scm_c_take_gc_bytevector): Rename this
  internal function, from scm_c_take_bytevector.  This indicates that
  unlike the other scm_take_* functions, this one takes GC-managed
  memory.

* libguile/objcodes.c (scm_objcode_to_bytecode):
* libguile/vm.c (really_make_boot_program): Use
  scm_gc_malloc_pointerless, not scm_malloc.  Thanks to Stefan
  Israelsson Tampe!

* libguile/r6rs-ports.c:
* libguile/strings.c: Adapt to renames.