Replace __page_size reference with PAGE_SIZE for android-12 and below

Also remove __getpageshift since it is not present in later version of
android (>12)

Bug: http://b/26475272
Bug: https://github.com/android-ndk/ndk/issues/1
Change-Id: I117194ede3b13a63ff020364b0f573fb25d5205d
4 files changed