more copy-editting from Josh

*** 39,79 ****
               amount allocated at minimum by each request.  Must be a power of
               2.
  
       afunc   A function which is called to import new spans from source, which
               may be NULL if this arena does not import from another.  When
!              calling vmem_create() afunc is an vmem_alloc_t a function taking
               three parameters and returning a pointer to void (the imported
               space):
  
               vmem_t *
                       The source arena from which we'll import.  The source
                       argument to vmem_create().
  
!              size_t  The size to import
  
               int     The vmflag argument used for the import.
  
!              When calling vmem_xcreate() afunc is an vmem_ximport_t a function
!              taking four parameters and returning a pointer to void (the
!              imported space):
  
               vmem_t *
                       The source arena from which we'll import.  The source
                       argument to vmem_xcreate().
  
               size_t *
!                      The size of the import, afunc may increase this size if
                       that is desirable, but must never decrease it.
  
               size_t  The desired alignment of the imported space.
  
!              int     the vmflag argument used for the import.
  
       ffunc   A function which is called to return spans to source, which may
               be NULL if this arena does not import from another.  This is a
!              vmem_free_t a function taking three parametes and returning void:
  
               vmem_t  The arena to which space is being returned.  The source
                       argument to vmem_create() or vmem_xcreate().
  
               void *  The span being returned to the source arena.
--- 39,80 ----
               amount allocated at minimum by each request.  Must be a power of
               2.
  
       afunc   A function which is called to import new spans from source, which
               may be NULL if this arena does not import from another.  When
!              calling vmem_create(), afunc is a vmem_alloc_t, a function taking
               three parameters and returning a pointer to void (the imported
               space):
  
               vmem_t *
                       The source arena from which we'll import.  The source
                       argument to vmem_create().
  
!              size_t  The size to import.
  
               int     The vmflag argument used for the import.
  
!              When calling vmem_xcreate(), afunc is a vmem_ximport_t, a
!              function taking four parameters and returning a pointer to void
!              (the imported space):
  
               vmem_t *
                       The source arena from which we'll import.  The source
                       argument to vmem_xcreate().
  
               size_t *
!                      The size of the import.  afunc may increase this size if
                       that is desirable, but must never decrease it.
  
               size_t  The desired alignment of the imported space.
  
!              int     The vmflag argument used for the import.
  
       ffunc   A function which is called to return spans to source, which may
               be NULL if this arena does not import from another.  This is a
!              vmem_free_t, a function taking three parameters and returning
!              void:
  
               vmem_t  The arena to which space is being returned.  The source
                       argument to vmem_create() or vmem_xcreate().
  
               void *  The span being returned to the source arena.