strip: Add --keep-section=SECTION and --remove-section=SECTION.

strip: Add --keep-section=SECTION and --remove-section=SECTION.

Adds two new output options:

  --keep-section=SECTION Keep the named section.  SECTION is an extended
                         wildcard pattern.  May be given more than once.

  --remove-section=SECTION   Remove the named section.  SECTION is an
                         extended wildcard pattern.  May be given more than
                         once.  Only non-allocated sections can be removed.

The --remove-section was already partially implemented, but only for the
.comment section. The short option -R is to be compatible with binutils.

The new testcase makes sure that various combinations of kept/removed
sections pull the correct dependencies into the output and/or debug files.

https://bugzilla.redhat.com/show_bug.cgi?id=1465997

Signed-off-by: Mark Wielaard <mark@klomp.org>