alpha: enhance decoding of getxpid, getxuid, and getxgid syscalls

Print the second return value of getxpid, getxuid, and getxgid syscalls
that return a pair of values using the same mechanism as pipe syscall.

* alpha.c: New file.
* Makefile.am (strace_SOURCES): Add it.
* linux/alpha/syscallent.h [20]: Change SEN(getpid) to SEN(getxpid).
[24]: Change SEN(getuid) to SEN(getxuid).
[47]: Change SEN(getgid) to SEN(getxgid).
* NEWS: Mention this enhancement.
* tests/uid.awk: Update for getxgid output change.
* tests/uid.test: Cleanup.
* tests/getxxid.c: New file.
* tests/getxxid.test: New test.
* tests/Makefile.am (check_PROGRAMS): Add getxxid.
(TESTS): Add getxxid.test.
* tests/.gitignore: Add getxxid.
diff --git a/alpha.c b/alpha.c
new file mode 100644
index 0000000..e343b7e
--- /dev/null
+++ b/alpha.c
@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2016 Dmitry V. Levin <ldv@altlinux.org>
+ * 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"
+
+#ifdef ALPHA
+
+static int
+decode_getxxid(struct tcb *tcp, const char *what)
+{
+	if (entering(tcp))
+		return 0;
+
+	long rval = getrval2(tcp);
+	if (rval == -1)
+		return 0;
+	static const char const fmt[] = "%s %ld";
+	static char outstr[sizeof(fmt) + 3 * sizeof(rval)];
+	snprintf(outstr, sizeof(outstr), fmt, what, rval);
+	tcp->auxstr = outstr;
+	return RVAL_STR;
+}
+
+SYS_FUNC(getxpid)
+{
+	return decode_getxxid(tcp, "ppid");
+}
+
+SYS_FUNC(getxuid)
+{
+	return decode_getxxid(tcp, "euid");
+}
+
+SYS_FUNC(getxgid)
+{
+	return decode_getxxid(tcp, "egid");
+}
+
+#endif /* ALPHA */