indenter mishandles multiline `match` clause body starting with literal value

[mbutterick]

If a match clause starts with a literal value, and the clause body goes onto a second line or more, those extra result lines are indented incorrectly.

#lang racket

(match 42
  [42 'this
      'that])

#lang at-exp racket

(match 42
  [42 'this
   'that])

[samth]

This also happens for case and cond.