Add check that map offset is sane to DexFile object init.

The DexFile constructor calls InitializeSectionsFromMapList, which
uses the header's map_offset before any checks are done on the file.

Bug: 37235346
Test: mm test-art-host-gtest-dex_file_test
Change-Id: I4fb8fcb57f9ef7e0182965b7ce663424b953abcb