devel/got: update to 0.76

User-visible changes:

• tog: extend log view author highlight colour to full field width
• tog: make headline highlight extend the full view width
• tog: add new log view limit feature to filter commits
• tog: respect current cursor position during log search
• tog: implement runtime help accessible via H,F1 keymaps
• add gotadmin init -b <branch> to specify repo head ref
• ensure got patch respects x-bit perms for new files
• show file mode for new added files in work tree diffs