Do Nodeprep on username and add Makefile

Makefile

@@ -0,0 +1,4 @@
+all: tests
+
+tests: test.m XMPPConnection.m XMPPStanza.m
+	objfw-compile -o $@ $^ -lidn -Wall -Werror

XMPPConnection.m

@@ -1,3 +1,5 @@
+#include <stringprep.h>
+#include <assert.h>
 #import "XMPPConnection.h"
 #import "XMPPStanza.h"
 
@@ -43,6 +45,27 @@
 	[super dealloc];
 }
 
+- (void)setUsername: (OFString*)username_
+{
+	OFString *old = username;
+	char *node;
+
+	Stringprep_rc rc;
+	if ((rc = stringprep_profile([username_ cString], &node, "Nodeprep", 0))
+			!= STRINGPREP_OK) {
+		of_log(@"Nodeprep failed: %s", stringprep_strerror(rc));
+		assert(0);
+	}
+
+	@try {
+		username = [[OFString alloc] initWithCString: node];
+	} @finally {
+		free(node);
+	}
+
+	[old release];
+}
+
 - (void)_startStream
 {
 	[sock writeFormat: @"<?xml version='1.0'?>\n"