gradle 2.14.1 to 4.7
build tools 21.1.2 to 27.0.3
build gradle 2.1.3 to 3.1.3

Patch received in https://github.com/matrix-org/olm/issues/13

Patch has been received by e-mail, Signed-off-by: Arnaud Fontaine <arnaud.fontaine@ssi.gouv.fr>

Signed-off-by: Sophie Taylor <sophie@spacekitteh.moe>

Add functions to make the difference between the native and the java code version.

Factor out the version management in the makefiles.