Make the asr API public. Install asr.h to /usr/include.h and manpages.

Include tweaks suggested by mpi@
ok deraadt@

src/include/Makefile

@@ -1,4 +1,4 @@
-#	$OpenBSD: Makefile,v 1.185 2014/03/24 19:09:14 kettenis Exp $
+#	$OpenBSD: Makefile,v 1.186 2014/03/26 18:13:15 eric Exp $
 #	$NetBSD: Makefile,v 1.59 1996/05/15 21:36:43 jtc Exp $
 
 #	@(#)Makefile	5.45.1.1 (Berkeley) 5/6/91
@@ -9,7 +9,7 @@
 
 .include <bsd.own.mk>
 
-FILES=	a.out.h ar.h assert.h bitstring.h blf.h bsd_auth.h \
+FILES=	a.out.h ar.h asr.h assert.h bitstring.h blf.h bsd_auth.h \
 	complex.h cpio.h ctype.h curses.h db.h dbm.h des.h dirent.h disktab.h \
 	dlfcn.h elf_abi.h err.h errno.h fenv.h float.h fnmatch.h fstab.h fts.h \
 	ftw.h getopt.h glob.h grp.h ifaddrs.h inttypes.h iso646.h kvm.h \

src/include/asr.h

@@ -0,0 +1,88 @@
+/*	$OpenBSD: asr.h,v 1.1 2014/03/26 18:13:15 eric Exp $	*/
+/*
+ * Copyright (c) 2012-2014 Eric Faurot <eric@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * Expected fd conditions
+ */
+#define ASR_WANT_READ	1
+#define ASR_WANT_WRITE	2
+
+/*
+ * Structure through which asynchronous query results are returned when
+ * calling asr_run().
+ */
+struct asr_result {
+	/* Fields set if the query is not done yet (asr_run returns 0) */
+	int	 ar_cond;	/* ASR_WANT_READ or ASR_WANT_WRITE */
+	int	 ar_fd;		/* the fd waiting for io condition */
+	int	 ar_timeout;	/* time to wait for in milliseconds */
+
+	/* Error fields.  Depends on the query type. */
+	int	 ar_errno;
+	int	 ar_h_errno;
+	int	 ar_gai_errno;
+	int	 ar_rrset_errno;
+
+	/* Result for res_*_async() calls */
+	int	 ar_count;	/* number of answers in the dns reply */
+	int	 ar_rcode;	/* response code in the dns reply */
+	void	*ar_data;	/* raw reply packet (must be freed) */
+	int	 ar_datalen;	/* reply packet length */
+	struct sockaddr_storage ar_ns; /* nameserver that responded */
+
+	/* Result for other calls. Must be freed properly. */
+	struct addrinfo	 *ar_addrinfo;
+	struct rrsetinfo *ar_rrsetinfo;
+	struct hostent	 *ar_hostent;
+	struct netent	 *ar_netent;
+};
+
+/*
+ * Asynchronous query management.
+ */
+
+/* Forward declaration. The API uses opaque pointers as query handles. */
+struct asr_query;
+
+int asr_run(struct asr_query *, struct asr_result *);
+int asr_run_sync(struct asr_query *, struct asr_result *);
+void asr_abort(struct asr_query *);
+
+/*
+ * Asynchronous version of the resolver functions. Similar prototypes, with
+ * an extra context parameter at the end which must currently be set to NULL.
+ * All functions return a handle suitable for use with the management functions
+ * above.
+ */
+struct asr_query *res_send_async(const unsigned char *, int, void *);
+struct asr_query *res_query_async(const char *, int, int, void *);
+struct asr_query *res_search_async(const char *, int, int, void *);
+
+struct asr_query *getrrsetbyname_async(const char *, unsigned int, unsigned int,
+    unsigned int, void *);
+
+struct asr_query *gethostbyname_async(const char *, void *);
+struct asr_query *gethostbyname2_async(const char *, int, void *);
+struct asr_query *gethostbyaddr_async(const void *, socklen_t, int, void *);
+
+struct asr_query *getnetbyname_async(const char *, void *);
+struct asr_query *getnetbyaddr_async(in_addr_t, int, void *);
+
+struct asr_query *getaddrinfo_async(const char *, const char *,
+    const struct addrinfo *, void *);
+struct asr_query *getnameinfo_async(const struct sockaddr *, socklen_t, char *,
+    size_t, char *, size_t, int, void *);