Swap argument order for file names and initargs in rrd create

src/lib/README.rrd.md

@@ -108,13 +108,13 @@ following keys defined:
    to be marked as known.  Defaults to `0.5`, indicating that at least
    half of corresponding PDPs must be marked as known.
 
-— Function **rrd.create_file** *arg* *filename*
+— Function **rrd.create_file** *filename* *arg*
 
 Create a new round-robin database as if calling `rrd.new` on *arg*, and
 then arrange for it to be mapped directly to *filename*.  Any subsequent
 update to the returned RRD database will be written to the file.
 
-— Function **rrd.create_shm** *arg* *name*
+— Function **rrd.create_shm** *name* *arg*
 
 Like **rrd.create_file**, but determining the file name by passing
 *name* to the `resolve` function of `core.shm`.

src/lib/rrd.lua

@@ -274,7 +274,7 @@ function new(arg)
    return open_mem(ptr, len)
 end
 
-function create_file(arg, filename)
+function create_file(filename, arg)
    local rrd = new(arg)
    local fd = assert(S.open(filename, "creat, rdwr, excl", '0664'))
    local f = file.fdopen(fd, 'wronly', filename)
@@ -286,10 +286,10 @@ function create_file(arg, filename)
    return open_mem(ptr, rrd.size)
 end
 
-function create_shm(arg, name)
+function create_shm(name, arg)
    local path = shm.resolve(name)
    shm.mkdir(lib.dirname(path))
-   return create_file(arg, shm.root..'/'..path)
+   return create_file(shm.root..'/'..path, name)
 end
 
 function dump(rrd, stream)