Disable macro redefined warnings on some includes.

The new kernel headers do:

  #define __bitwise __bitwise__

However, the code redefines __bitwise without undef'ing it first.

The files affected are the include files from external/e2fsprogs,
so the warnings will only be disabled around those includes.

This is a temporary fix, b/35721782 filed to fix this.

Test: Builds without warningers/errors.
Change-Id: I2eae12558c23be9bb3bf3931467b32eee5d57720