rename libc to libjehanne; improve libposix

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

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

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2015 Giacomo Tesio <giacomo@tesio.it>
+ *
+ * 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>
+
+void
+jehanne_lock(Lock *l)
+{
+	if(jehanne_ainc(&l->key) == 1)
+		return;	/* changed from 0 -> 1: we hold lock */
+	/* otherwise wait in kernel */
+	while(sys_semacquire(&l->sem, 1) < 0){
+		/* interrupted; try again */
+	}
+}
+
+void
+jehanne_unlock(Lock *l)
+{
+	if(jehanne_adec(&l->key) == 0)
+		return;	/* changed from 1 -> 0: no contention */
+	sys_semrelease(&l->sem, 1);
+}
+
+int
+jehanne_canlock(Lock *l)
+{
+	if(jehanne_ainc(&l->key) == 1)
+		return 1;	/* changed from 0 -> 1: success */
+	/* Undo increment (but don't miss wakeup) */
+	if(jehanne_adec(&l->key) == 0)
+		return 0;	/* changed from 1 -> 0: no contention */
+	sys_semrelease(&l->sem, 1);
+	return 0;
+}
+
+int
+jehanne_lockt(Lock *l, uint32_t ms)
+{
+	if(jehanne_ainc(&l->key) == 1)
+		return 1;	/* changed from 0 -> 1: we hold lock */
+	/* otherwise wait in kernel */
+	return jehanne_tsemacquire(&l->sem, ms);
+}