Add V.34 option for ModemStandard directive

Add some " to synch with 2.4.x and fix color highlight in online doc.

("i-was-rich-and-got-a-leased-line" is still undocumented, but do we really need to document it?)

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1731351 13f79535-47bb-0310-9956-ffa450edef68