base/binutils: Cleanup packing lists.

[jhb]

Summary

• Use BUREMOVE to strip binutils tools not installed by the base/binutils package.
• Update BUREMOVE logic in devel/binutils to cope with the base package which installs tools without a BUTARGET- prefix.
• Use MANPREFIX for BUREMOVE to handle the PREFIX=/usr case used by base/binutils.
• Remove binutils headers and libraries explicitly from the staging area for base/binutils.
• Add missing plist entries for binutils binaries installed under a BUTARGET subdirectory.
• Drop plist entries from devel/binutils that are now properly removed. Previously the binaries for Windows tools like dlltool were removed from the staging area but the manpages were still left in the package.

This is a recommit of r476186 but with the update to the pkg-plist of
devel/binutils.

PR: 230278

Test Plan

• poudriere testport of devel/binutils, devel/amd64-binutils
• make check-plist of base/binutils for amd64 and i386

[jhb]

Ping. I'd really like to have this one reviewed rather than relying on maintainer timeout since the previous version broke the build.

[antoine]

PORTREVISION has to be bumped