dahdi: Restore DAHDI_CONFLINK functionality as compile time option.

This is mostly a revert of commit r9463. If you need to use DAHDI_CONFLINK
ioctl, make sure to define CONFIG_DAHDI_CONFLINK in
include/dahdi/dahdi_config.h. Apparently there were some users of CONFLINK out
there still.

It's a compile time option now since most users won't need to run the test for
conflinks in the hot-path that is the process_masterspan function.

Signed-off-by: Shaun Ruffell <sruffell@digium.com>
Tested-by: Ted Gerold <ted@twg.org>

include/dahdi/dahdi_config.h

@@ -190,4 +190,10 @@
  */
 /* #define CONFIG_DAHDI_MIRROR */
 
+/*
+ * Adds support for conference links. There are some non-Asterisk users of this
+ * functionality.
+ */
+/* #define CONFIG_DAHDI_CONFLINK */
+
 #endif

include/dahdi/user.h

@@ -636,6 +636,11 @@ struct dahdi_confinfo {
 #define DAHDI_SETCONF_V1		_IOW(DAHDI_CODE,  12, struct dahdi_confinfo)
 #define DAHDI_SETCONF			_IOWR(DAHDI_CODE, 13, struct dahdi_confinfo)
 
+/*
+ * Setup or Remove Conference Link
+ */
+#define DAHDI_CONFLINK			_IOW(DAHDI_CODE, 14, struct dahdi_confinfo)
+
 /*
  * Display Conference Diagnostic Information on Console
  */