hostaliases: add

I don't know why, but I had it in .git/info/excludes for a long time.
README: add missing header
install: style fixes
install: prefix .files with 'old_' when trashing
install: use ~/tmp as trash

I do not have ~/Trash anymore; ~/tmp kind of took over. :(
install: do not link .gvimrc

$GVIMINIT will suffice.
install: style fixes
install: reorder function declarations by usage
install: document the mysterious sha1sums