doc:  clarify that auth. names are lower case and case-sensitive
This is true even for acronyms that are usually upper case, like LDAP.
Reported-by: Alvaro Herrera
Discussion:
Backpatch-through: 10
@@ -413,7 +413,9 @@ hostnogssenc <replaceable>database</replaceable> <replaceable>user</replaceabl
<para>
Specifies the authentication method to use when a connection matches
this record. The possible choices are summarized here; details
- are in <xref linkend="auth-methods"/>.
+ are in <xref linkend="auth-methods"/>. All the options
+ are lower case and treated case sensitively, so even acronyms like
+ <literal>ldap</literal> must be specified as lower case.
<variablelist>
<varlistentry>
