DWARF 2 has 9 standard opcodes, so dwarfdump expects us to use an
opcode base of at least 10. Previously we used 5.

Discussion:
https://groups.google.com/forum/#!topic/golang-dev/d-BqpPgalzc

LGTM=josharian, rsc
R=golang-codereviews, gobot, rsc, josharian, iant, bradfitz
CC=golang-codereviews
https://golang.org/cl/69320043