Build system improvements

[Jeremie Koenig]

Hello, me again, these patches are related to the build system.

The first three actually have an effect:

[PATCH 1/7] Fix the build system to handle part stores
[PATCH 2/7] Fix the way FOOFLAGS is handled
[PATCH 3/7] Update ./configure (you may want to do this yourself)

The latter ones are cleanups:

[PATCH 4/7] Makeconf: remove redundant $($*-FOOFLAGS)
[PATCH 5/7] Makeconf: simplify the directory logic
[PATCH 6/7] Makeconf: let config.make define $(configured)
[PATCH 7/7] Makeconf: simplify the decoding of $(makemode)

Let me know what you think,