libexif: Add exif-compat.c for backwards compatibility

Older camera HALs call on libexif, and with the name change to libjhead here:
https://android.googlesource.com/platform/external/jhead/+/acbfc9c1c7e1a84b0db4dc5bc3d5346b6c55c473

It cannot find the necessary functions/symbols. Add exif-compat.c to call on these functions
using dynamic linking.

Special thanks goes out to Ryuinferno who thoroughly tested this and is the co-author.

Change-Id: I53c9c32e8467af845ad18dc689a9adde4bb4a1b2