"else if" in "for" and "else switch"

[CeylonMigrationBot]

[@gavinking] Issue #4557 begs the question of whether I should be allowed to:

• write else if on a for, and/or
• write else switch.

These are minor parser-level changes.

[Migrated from ceylon/ceylon-spec#1452]

[CeylonMigrationBot]

[@lucaswerkmeister] This just looks like a random selection of keyword-keyword combinations to me. Why else switch but not else for and else while? And what’s wrong with blocks that you suddenly seem to want to avoid them like the plague?