more copy-editting from Josh

@@ -39,41 +39,42 @@
              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
+             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
+             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):
+             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
+                     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.
+             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_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.