all: fix a few spelling errors in source comments

src/cmd/gc/fmt.c

src/cmd/gc/go.h

src/cmd/gc/subr.c

src/cmd/nm/doc.go

src/liblink/asm5.c

src/pkg/database/sql/sql.go

src/pkg/sort/sort.go

test/divmod.go

test/fixedbugs/bug476.go

test/run.go