thread_setaffinity: Allow affinity param to have a length less than cpumask_size()

[squeek502]

Instead of enforcing that the table length is >= cpumask_size(), any missing CPU numbers get assigned an affinity of false. This makes this API a bit more user-friendly, since users no longer have to initialize a table of length cpumask_size() before setting the particular affinities they actually want.

As an example, before this commit, you'd have to do something like:

local affinity = {}
for i=1,uv.cpumask_size() do
  affinity[i] = false
end
affinity[3] = true
affinity[5] = true

But after this commit, this table:

local affinity = { [3] = true, [5] = true }

will now be accepted and all the missing keys up to uv_cpumask_size() will be treated as false in the thread_setaffinity call.

[zhaozg]

Just minor comments

[squeek502]

I can't see your comments

[zhaozg]

Mainly because lua_rawlen of a table(not array) will return 0.

From 415 line

  int min_mask_size = uv_cpumask_size();
  if (min_mask_size < 0) {
    return luv_error(L, min_mask_size);
  }
  int mask_size = lua_rawlen(L, 2);
  if (mask_size < min_mask_size) {
    mask_size = min_mask_size;
  }
  char* cpumask = malloc(mask_size);

can be simplify to

  int mask_size = uv_cpumask_size();
  if (mask_size < 0) {
    return luv_error(L, mask_size);
  }
  char* cpumask = malloc(mask_size);

[zhaozg]

LGTM.