Add strspn() to libkern.

Ok'ed by:	rwatson

sys/conf/files

@@ -1252,6 +1252,7 @@ libkern/strlen.c		standard
 libkern/strncmp.c		standard
 libkern/strncpy.c		standard
 libkern/strsep.c		standard
+libkern/strspn.c		standard
 libkern/strtol.c		standard
 libkern/strtoq.c		standard
 libkern/strtoul.c		standard

sys/libkern/strspn.c

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 1989, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/libkern.h>
+
+/*
+ * Span the string s2 (skip characters that are in s2).
+ */
+size_t
+strspn(s1, s2)
+	const char *s1;
+	const char *s2;
+{
+	const char *p = s1, *spanp;
+	char c, sc;
+
+	/*
+	 * Skip any characters in s2, excluding the terminating \0.
+	 */
+cont:
+	c = *p++;
+	for (spanp = s2; (sc = *spanp++) != 0;)
+		if (sc == c)
+			goto cont;
+	return (p - 1 - s1);
+}

sys/sys/libkern.h

@@ -105,6 +105,7 @@ size_t	 strlen(const char *);
 int	 strncmp(const char *, const char *, size_t);
 char	*strncpy(char * __restrict, const char * __restrict, size_t);
 char	*strsep(char **, const char *delim);
+size_t	 strspn(const char *, const char *);
 int	 strvalid(const char *, size_t);