Fix multiple errors spawning for the same token.

[irevoire]

Fix #260

Hey, basically, my error was that when we encountered a trailing error, we were still supposed to recover from it (by eating all the tokens until the end of the line), but I missed it in my first implementation.
So, this PR fixes it and adds a test for it.

[sharkdp]

Thank you very much!

This still has problems in edge cases where expression/statements span multiple lines, but I think that is okay (see below). This PR is definitely an improvement.

>>> if 2 < 3 +
  then 4
  else 5 +
error: while parsing
  ┌─ <input:12>:1:11
  │  
1 │   if 2 < 3 +
  │ ╭──────────^
2 │ │   then 4
  │ ╰^ Expected one of: number, identifier, parenthesized expression

error: while parsing
  ┌─ <input:12>:2:3
  │
2 │   then 4
  │   ^^^^ Expected one of: number, identifier, parenthesized expression

error: while parsing
  ┌─ <input:12>:3:3
  │
3 │   else 5 +
  │   ^^^^ Expected one of: number, identifier, parenthesized expression