tests: re-enable dead_code_elimination test.

... and adapted a test of inifnite-loops.

rdar://problem/34013900

Author: eeckstein

test/SILOptimizer/dead_code_elimination.sil

@@ -1,7 +1,5 @@
 // RUN: %target-sil-opt -assume-parsing-unqualified-ownership-sil -enable-sil-verify-all -dce %s | %FileCheck %s
 
-// REQUIRES: rdar34013900
-
 sil_stage canonical
 
 import Builtin
@@ -59,17 +57,15 @@ bb3:
   return %18 : $()
 }
 
-// We currently bail out on functions that have structurally infinite
-// loops.
 // CHECK-LABEL: sil @dead3
 sil @dead3 : $@convention(thin) () -> () {
 bb0:
 // CHECK: bb0
   br bb1
 // CHECK: bb1
 bb1:
-// CHECK: integer_literal $Builtin.Int32, 0
-// CHECK: br bb1
+// CHECK:      bb1:
+// CHECK-NEXT:   br bb1
   %0 = integer_literal $Builtin.Int32, 0
   br bb1
 }