configure.ac: bump version to 1.5.93 for rc2
configure.ac: bump version to 1.5.93 for rc2

Signed-off-by: Pekka Paalanen <0f6ae7001e34c37b02fb2c1c2573ddf8f442136a@collabora.co.uk>

sir-murray/wayland,bitfactor/wayland,abooij/wayland,bitfactor/wayland,abooij/wayland,sir-murray/wayland,tulcod/wayland,eyolfson/wayland,abooij/wayland,sir-murray/wayland,mchalupa/wayland,bitfactor/wayland,mchalupa/wayland,mchalupa/wayland,tulcod/wayland,tulcod/wayland,eyolfson/wayland,eyolfson/wayland