ejabberdctl: Omit su(1)'s "-p" flag

On Linux, su(1)'s "-p" flag makes sure the following environment
variables are preserved: $HOME, $SHELL, $USER, and $LOGNAME.  The flag
isn't portable, and since we don't set HOME=$SPOOLDIR anymore, there's
no reason to preserve these variables anyway.

Without "-p", we also don't need to set HOME=$INSTALLUSER_HOME, as su(1)
now does that for us.
Apply minor improvement to ejabberd.yml comment
Mention "starttls_required" option in ejabberd.yml

Closes #258.
Remove "--enable-http" flag

Specifying the "--enable-http" flag on the ./configure command line had
no effect.
Merge pull request #264 from weiss/su-without-p

ejabberdctl: Omit su(1)'s "-p" flag
Merge pull request #265 from weiss/mention-starttls-required

Mention "starttls_required" option in sample configuration file
Merge pull request #266 from weiss/remove-http

Remove "--enable-http" flag
Reorganize mod_announce test in order to avoid race
doc/Makefile: Replace non-portable echo(1) calls

The echo(1) behavior is system-dependent, the printf(1) behavior is not.
typo fix on roster subscription (EJAB-1711)
mod_offline now uses gen_server
Merge pull request #267 from weiss/replace-echo-calls

doc/Makefile: Replace non-portable echo(1) calls
Log auth method for incoming s2s connections

Generate an [info] message that logs whether an incoming s2s connection
is authenticated using the SASL EXTERNAL mechanism or via Server
Dialback.  While at it, also mention whether TLS is enabled.
Merge pull request #270 from weiss/log-s2s-in-auth

Log authentication method for incoming s2s connections
Fix odbc update_t and update insert case return value
Merge pull request #1 from vesvalo/master

Fix odbc update_t and update insert case return value
fix mod_offline to store only chat messages with body xml element
Merge pull request #2 from vesvalo/master

fix mod_offline to store only chat messages with body xml element
Merge pull request #273 from gamenet/master

odb_queries patch return value of functions update and update_t in case of sql insert
Do not call functions from ejabberd_riak directly