strict: fix some strict-mode fails

Some tests that fail when run in strict mode:

## Fixed by this patch
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-114 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-204 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-30 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-88 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-89 in strict mode

## Still failing, will fix 
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-115 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-163 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-164 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-176 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-177 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-197 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-199 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-44 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-57 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-67 in strict mode
  ch15\15.2\15.2.3\15.2.3.7\15.2.3.7-6-a-75 in strict mode

We'll need something else to support ES6 Symbols or need to document that this function won't work for Symbol valued property keys.