[moonc][linter] alternative output

[ildar]

that's easy to process automatically. GCC-like:

$  tl check test.lua
========================================
3 warnings:
test.lua:1:7: unknown variable: square
test.lua:2:19: unknown variable: x
test.lua:5:1: unknown variable: console

Also this is not clear even for a human:

$  moonc-5.4 -l test.moon
test.moon
Failed to parse:
 [3] >>    1 = =

(This means the problematic line is 3)