ldirectord: minor documentation cleanup and tweaks

The patch below removes superfluous headings, renders option names in bold, and rephrases the sentence dealing with IPv6 literal addresses.

```
--- ldirectord/ldirectord.in.orig 2013-02-07 13:17:42.000000000 +0100
+++ ldirectord/ldirectord.in 2013-12-17 13:32:04.450002165 +0100
@@ -424,7 +424,6 @@
the IP-address and port of the real server is overridden, otherwise the
IP-address and port of the real server is used.

-=head2
For TCP and UDP (non fwmark) virtual services, unless the forwarding method
is B and the IP address of a real server is non-local (not present on
a interface on the host running ldirectord) then the port of the real
@@ -433,10 +432,9 @@
method is B. This is due to the way that the underlying LVS code in
the kernel functions.

-=head2
More than one of these entries may be inside a virtual section. The
-checktimeout, negotiatetimeout, checkcount, fallback, emailalert,
-emailalertfreq and quiescent options listed above may also appear inside a
+B, B, B, B, B,
+B and B options listed above may also appear inside a
virtual section, in which case the global setting is overridden.

B

Review ldirectord/ldirectord.in against the supplied diff, focusing on the option formatting, removed headings, and the IPv6 literal-address wording. Confirm the documentation renders correctly and that all requested wording changes are present; no test or separate entry point is named.

Written by the indexing model from the issue text.