These are likely from the time when gc was written in C. There is no
need for any of these to be passed pointers, as the previous values are
not kept in any way, and the pointers are never nil. Others were left
untouched as they fell into one of these useful cases.

While at it, also turn some 0/1 integers into booleans.

Passes toolstash -cmp on std cmd.

Change-Id: Id3a9c9e84ef89536c4dc69a7fdbacd0fd7a76a9b
Reviewed-on: https://go-review.googlesource.com/72990
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>