if an object in an archive tries to refer
to a file in its original source directory,
ignore it.
* 6ar:
fix bug if archive is empty.
* gobuild:
build archive in current directory.
* math:
use new gobuild Makefile.
* test/math.go:
rename to mathest.go, add // run line, make it run.
R=r
DELTA=494 (277 added, 203 deleted, 14 changed)
OCL=19090
CL=19171
