SASL support

The only supported methods are PLAIN and EXTERNAL, the latter is untested as of
now.
The code gets the values from the keys named sasl_{mechanism,username,password}
specified for each chatnet.

src/irc/core/sasl.h

@@ -0,0 +1,14 @@
+#ifndef __SASL_H
+#define __SASL_H
+
+enum {
+	SASL_MECHANISM_NONE = 0,
+	SASL_MECHANISM_PLAIN,
+	SASL_MECHANISM_EXTERNAL,
+	SASL_MECHANISM_MAX
+};
+
+void sasl_init(void);
+void sasl_deinit(void);
+
+#endif