- Option for mmake to run it in the current directory only for some
target (still considering all deps).

- Allow to continue #MM lines

- Allow to specify a meta rule for which mmake doesn't call make
(ie. mmake will not try to run make on the makefile which contains this
metatarget) to avoid "Nothing known about <metatarget>".

- MetaMake should convert the source makefiles into makefiles while
searching for metatargets. This would allow to modify the metatargets
on the fly !
