During troubleshooting it's very convenient to know the exact version
used in a bug report. With the git commit SHA1 added to the version
string in all builds, that becomes very easy.
Add a basic Android.mk for building with the Android NDK. This can serve
as a good starting point for developers integrating libdivecomputer into
an Android application.
Co-authored-by: Sven Knoch <info@divinglog.de>