Revert "[asan] Use dynamic shadow on 32-bit Android" and 3 more.

Revert the following commits:
  r318369 [asan] Fallback to non-ifunc dynamic shadow on android<22.
  r318235 [asan] Prevent rematerialization of &__asan_shadow.
  r317948 [sanitizer] Remove unnecessary attribute hidden.
  r317943 [asan] Use dynamic shadow on 32-bit Android.

MemoryRangeIsAvailable() reads /proc/$PID/maps into an mmap-ed buffer
that may overlap with the address range that we plan to use for the
dynamic shadow mapping. This is causing random startup crashes.

llvm-svn: 318575