Introduce libstrace.a for potentially conditional compilation units

Some files are used conditionally depending on architecture and
configuration.  Create a library for the purpose of keeping such
compilation units.

* Makefile.am (strace_LDADD, noinst_LIBRARIES): Add libstrace.a.
(libstrace_a_CPPFLAGS): New variable, set to $(strace_CPPFLAGS).
(libstrace_a_CFLAGS): New variable, set to $(strace_CFLAGS).
(libstrace_a_SOURCES): New variable, set to upeek.c.
* util.c (upeek): Move ...
* upeek.c: ... here.
diff --git a/upeek.c b/upeek.c
new file mode 100644
index 0000000..f4f20bb
--- /dev/null
+++ b/upeek.c
@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 1991, 1992 Paul Kranenburg <pk@cs.few.eur.nl>
+ * Copyright (c) 1993 Branko Lankester <branko@hacktic.nl>
+ * Copyright (c) 1993, 1994, 1995, 1996 Rick Sladkey <jrs@world.std.com>
+ * Copyright (c) 1996-1999 Wichert Akkerman <wichert@cistron.nl>
+ * Copyright (c) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
+ *                     Linux for s390 port by D.J. Barrow
+ *                    <barrow_dj@mail.yahoo.com,djbarrow@de.ibm.com>
+ * 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.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 "defs.h"
+#include "ptrace.h"
+
+int
+upeek(int pid, long off, long *res)
+{
+	long val;
+
+	errno = 0;
+	val = ptrace(PTRACE_PEEKUSER, (pid_t)pid, (char *) off, 0);
+	if (val == -1 && errno) {
+		if (errno != ESRCH) {
+			perror_msg("upeek: PTRACE_PEEKUSER pid:%d @0x%lx)", pid, off);
+		}
+		return -1;
+	}
+	*res = val;
+	return 0;
+}