Fix _really_ nasty typo

It was especially nasty, because, half of the time, the result is what
you'd expect.
Prevent ws_Statement_deinit from deinit'ing *NULL
Add support for implicit arguments

The idea is that you can pass a number like so:

    { "add": 4 }

Which adds the four last numbers on the stack.
Fix type of buffer var

If we internally use intmax_t, but the buffer used for transmission is
an uin32_t, we end up with completely different values for negative
and/or big numbers.
Merge pull request #342 from matthiasbeyer/add-support_for_implicit_arguments

Support for implicit arguments
Merge pull request #343 from neithernut/fix-union_int-assignment

Fix type of buffer var