main.c: 1.81->1.82

main.c: 1.81->1.82
Author: imp
Log:
No need to check to see if we're running a version of FreeBSD 3.0 current or
newer anymore.

cond.c: 1.26->1.27
Author: imp
Log:
Keep up with minor changes to NetBSD.  Consider a variable empty when
not define.

Obtained From: NetBSD (rev 1.18; sjg)

for.c: 1.19->1.20
Author: ru
Log:
Command line variables take precedence over global variables.
Make this true in the .for loops too.  The following fragment,

        FOO=    foo bar

        all:
        .for f in ${FOO}
                @echo ${f}
        .endfor

when run as "make FOO=xxx" should print "xxx".  (OpenBSD had
this bug fixed for some time.)

Obtained-from: FreeBSD
Submitted-by: Max Okumoto <okumoto@ucsd.edu>