This commit reviews all continue uses in core happening within a
loop / switch / case hierarchy. This does not cover:

- Changes to libraries. Will be handled in another issue / commit.
- Uses out from loops, will be reviewed by other commit.

The policy followed has been:
- When possible, take rid of the continue.
- When clearly the intention was to jump to next element in loop
  change to continue 2
- When it was not clear, keep old behavior switching to break, no
  matter how weird the behavior may be.