cmd/ld: remove Plan 9 symbol table
Update #6853
Nothing reads the Plan 9 symbol table anymore.
The last holdout was 'go tool nm', but since being rewritten in Go
it uses the standard symbol table for the binary format
(ELF, Mach-O, PE) instead.
Removing the Plan 9 symbol table saves ~15% disk space
on most binaries.
Two supporting changes included in this CL:
debug/gosym: use Go 1.2 pclntab to synthesize func-only
symbol table when there is no Plan 9 symbol table
debug/elf, debug/macho, debug/pe: ignore final EOF from ReadAt
LGTM=r
R=r, bradfitz
CC=golang-codereviews
https://golang.org/cl/
65740045