ui-log: add support for showing the full commit message

Some users prefer to see the full message, so to make these users happy
the new querystring parameter "showmsg" can be used to print the full
commit message per log entry.

A link is provided in the log heading to make this function accessible,
and all links and forms tries to preserve the users preference.

Note: the new link is not displayed on the summary page since the point
of the summary page is to be a summary, but it is still obeyed if specified
manually.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

cgit.c

@@ -154,6 +154,8 @@ static void querystring_cb(const char *name, const char *value)
 		ctx.qry.name = xstrdup(value);
 	} else if (!strcmp(name, "mimetype")) {
 		ctx.qry.mimetype = xstrdup(value);
+	} else if (!strcmp(name, "showmsg")) {
+		ctx.qry.showmsg = atoi(value);
 	}
 }