Fix setting of map_offset in frame data.

The old code set the map_offset from elf_offset, but it should have used
offset. Without this change, frame data is not properly shown for shared
libraries in an apk.

Add new unit test to verify that map_offset is set properly.

Test: Ran new unit tests.
Change-Id: I2fe5abda23a5de51c8fcf9361ba9350b80446f15