devel/got: update to 0.87

User-visible changes:

• tog: resume blame and diff search from the first line
• fix rebase/histedit -a leaving some files on the temporary branch
• make 'got revert' and 'got rm' work on non-existent directories
• when aborting rebase/histedit/merge, unlink files added by merged changes
• allow no-op merge commits to be created
• fix sending merge commits
• show how to fetch a pull request in got.1 pull request example section