Sequence with embedded colon confuses parser

[stevedonovan]

I noticed this when parsing docker-compose.yml files, which have things like this:

    ports:
      - 172.17.0.1:19000:19000

Where the item is to be considered a string. Generally a colon without a following space is ignored in these situations.

We go wrong at line 513 in parseseq:

    if sfind(rest, '^[^\'\"%s]*:') then
      -- Inline nested hash
      local indent2 = j
      lines[1] = string.rep(' ', indent2)..rest
      tinsert(seq, parsemap('', lines, indent2))

The minimal fix is simple - insist that there is a space after the colon:

    if sfind(rest, '^[^\'\"%s]*:%s') then

I couldn't find any tests for 'inline nested hash' so I don't know if it continues to do that job.