rename libc to libjehanne; improve libposix

This is to avoid conflicts between standards' assumptions and Jehanne's choices

sys/src/lib/jehanne/port/utfutf.c

@@ -0,0 +1,35 @@
+/*
+ * This file is part of the UCB release of Plan 9. It is subject to the license
+ * terms in the LICENSE file found in the top-level directory of this
+ * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
+ * part of the UCB release of Plan 9, including this file, may be copied,
+ * modified, propagated, or distributed except according to the terms contained
+ * in the LICENSE file.
+ */
+
+#include <u.h>
+#include <libc.h>
+
+
+/*
+ * Return pointer to first occurrence of s2 in s1,
+ * 0 if none
+ */
+char*
+jehanne_utfutf(const char *s1, const char *s2)
+{
+	const char *p;
+	int32_t f, n1, n2;
+	Rune r;
+
+	n1 = jehanne_chartorune(&r, s2);
+	f = r;
+	if(f <= Runesync)		/* represents self */
+		return jehanne_strstr(s1, s2);
+
+	n2 = jehanne_strlen(s2);
+	for(p=s1; p=jehanne_utfrune(p, f); p+=n1)
+		if(jehanne_strncmp(p, s2, n2) == 0)
+			return (char*)p;
+	return 0;
+}