Fix builds with jam on VMS:
The Jambase itself was not formatting the CCHDRS and CCDEFS
properly: on VMS they can't be appended to, because multiple
/define or /include directives don't work. Instead now
CCHDRS and CCDEFS is reformatted from HDRS and DEFINES anytime
those latter two change. This requires the recent change to
jam to allow access to target-specific variables when setting
other variables.
=== computer.perforce.com:1666: Change 21443 by PERFORCE@vulgar on 2001/03/23 12:22:17
Noted as VMS porting change in the RELNOTES. - rmg