Rewrite libdexfile C API to follow NDK guidelines better. Bug: 123517037 Bug: 145347927 Test: test-art-host-gtest-art_libdexfile_support_tests64 Test: test-art-host-gtest-art_libdexfile_external_tests64 Change-Id: I9673872585456937d2f54abb63e3dbd8aad4e9ad