Add gpm (general purpose mouse) server package

[Peter: small white space fixes as pointed out by Yann]
Signed-off-by: Julien Boibessot <julien.boibessot@armadeus.com>
Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>