Move scandir_b to a later symbol version.
FreeBSD make (aka fmake) doesn't grok .MAKE.LEVEL. Failsafe and assume
that it is OK to set MK_xxx flags.
Move setting of the MK_xxx variables based on NO_xxx to avoid
triggering the "you aren't allowed to set this" warning when building
stand alone in directories whose Makefile sets NO_MAN, for example.