cmd/ld: fix syms that are both cgo_import_static & cgo_import_dynamic

This is needed for SWIG when linking in internal mode.  In
internal mode if a symbol was cgo_import_static we used to
forget that it was also cgo_import_dynamic.

R=rsc, r
CC=golang-dev
https://codereview.appspot.com/9080043
runtime/cgo: export symbols in both internal and external link mode

R=rsc, r
CC=golang-dev
https://codereview.appspot.com/9060045
cmd/cgo: correct pragma name in comment

R=rsc, alexb, minux.ma, bradfitz, i.caught.air
CC=golang-dev
https://codereview.appspot.com/9082043
libmach: fix build on Plan 9

Include libc.h before bio.h in 8.c, because bio.h uses
the UTFmax enum, which is declared in libc.h, since
the recent switch to 21-bit runes in Plan 9.

The 5.c and 6.c files already includes libc.h.

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/9040047

Committer: Rob Pike <r@golang.org>
cmd/ld: fix another unsigned value causing bugs on Plan 9
"The usual conversions" bite again.

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/9103044
cmd/ld: fix SDYNIMPORT symbol test

As advised by iant. Fixes windows build.

R=golang-dev, r
CC=golang-dev, iant
https://codereview.appspot.com/9110044
doc: only U+FEFF is a byte-order mark; U+FFFE is not

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/9103046