Update malloc.h

Remove functions never implemented in bionic from malloc.h

Related CLs:
  https://android-review.googlesource.com/#/c/41728
  https://android-review.googlesource.com/#/c/41731
  https://android-review.googlesource.com/#/c/41717

Change-Id: I06639071e3fb442e2389a932382a88a7318606b9
1 file changed