CMake: Fix build with unversion_libname configuration

a162a3cb (Android: Add "unversioned_libname" configuration, 2014-04-23)
removed the version for shared libs on Android. This change updates
the generated CMake files to support that.

Change-Id: Ia6ef04872c664bd4c31546456a82730babed2910
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
Do not resolve the java functions for each call

Instead do it only once (in registerNatives). This is seems to be the
preferred way of doing it in other parts of the platform plugin.

Change-Id: I361a7862bb5a24b4024c7c6a30ecb14fc515d4ff
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>