On the machine I'm using, the hardware page size seems to be 64 kB.
Make ELF rounding and mmap quantum 64 kB to match.
Error numbers returned from kernel are positive; do not negate.
Implement stubs for math/big.
LGTM=minux
R=minux
CC=golang-codereviews
https://golang.org/cl/124300043
No modifications other than adding copyright header to each file, and
concatenating several cmd/9l files together to form the liblink files.
LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://golang.org/cl/123840043