Specifically intended for removing -fschg ("INSTALLFLAGS_EDIT=:S/schg/uchg/")
this makes the NOFSCHG flag redundant. NOFSCHG will still be honoured by
bsd.lib.mk but is valid for buildworld only. NOFSCHG is still implemented in
the old way (ie. _not_ ".if NOFSCHG then { INSTALLFLAGS_EDIT+=:S/schg/,/ }"
to emphasize the fact that NOFSCHG is only supported in a limited
fashion and for buildworld.
The interface and implementation are such that future use of flags such
as sappnd can also be easily removed or altered (perhaps to uappnd).
This commit brought to you by the letters B, D, and E, and the numbers six,
one, thirteen, and three.