doc/installation: convert dependency table to dsv format
The dependency table was originally in "fixed" format, so that
AsciiDoc took a fixed number of characters to the first column
and the rest to the second column. However, "OpenSSL or GNU TLS
or nss_compat_ossl" will not fit in that number of characters,
and backslash line continuation will not help because AsciiDoc
apparently parses that before it counts the characters.
I could widen the column in the AsciiDoc source but switching
to "dsv" format seems prettier.