new syscall package: manually maintained files and scripts.

auto-generated files and deletions are in another CL.

goals for new syscall:
	* automate as much as possible
	* do not let clients do unsafe things
	* use simple types (int not int64)
	* fewer files

the files are renamed from foo_amd64_linux to foo_linux_amd64,
both because it reads better (all the linux are related, all the amd64 less so)
and because it made it easier to replace the existing ones.

R=r
DELTA=2336  (2260 added, 6 deleted, 70 changed)
OCL=29709
CL=29723

src/lib/syscall/errstr.go

@@ -0,0 +1,30 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package syscall
+
+import "syscall"
+
+func str(val int) string {  // do it here rather than with fmt to avoid dependency
+	if val < 0 {
+		return "-" + str(-val);
+	}
+	var buf [32]byte;  // big enough for int64
+	i := len(buf)-1;
+	for val >= 10 {
+		buf[i] = byte(val%10 + '0');
+		i--;
+		val /= 10;
+	}
+	buf[i] = byte(val + '0');
+	return string(buf[i:len(buf)]);
+}
+
+func Errstr(errno int) string {
+	if errno < 0 || errno >= int(len(errors)) {
+		return "error " + str(errno)
+	}
+	return errors[errno]
+}
+