allow user to override MFSROOT_FREE_*
allow user to override MFSROOT_FREE_*

when you add many files to mfsroot, you need to bump these values.

mmatuska/mfsbsd,meganuke19/mfsbsd,solobsd/SoloBSD,solobsd/SoloBSD,johnko/mfsbsd,meganuke19/mfsbsd,johnko/mfsbsd,mmatuska/mfsbsd,DaElf/mfsbsd,DaElf/mfsbsd