menu-cache: new package

[Thomas:
  - Remove the MENU_CACHE_VERSION_MINOR variable, not needed. Noticed
    by Yann E. Morin.
  - Rewrap Config.in help text.]

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>