cleanup: rename package and vendor dependencies for old go versions

Fixes #8 and begins to address deployability.

vendor/github.com/pebbe/zmq4/errors.go

@@ -0,0 +1,92 @@
+package zmq4
+
+/*
+#include <zmq.h>
+*/
+import "C"
+
+import (
+	"syscall"
+)
+
+// An Errno is an unsigned number describing an error condition as returned by a call to ZeroMQ.
+// It implements the error interface.
+// The number is either a standard system error, or an error defined by the C library of ZeroMQ.
+type Errno uintptr
+
+const (
+	// Error conditions defined by the C library of ZeroMQ.
+
+	// On Windows platform some of the standard POSIX errnos are not defined.
+	EADDRINUSE      = Errno(C.EADDRINUSE)
+	EADDRNOTAVAIL   = Errno(C.EADDRNOTAVAIL)
+	EAFNOSUPPORT    = Errno(C.EAFNOSUPPORT)
+	ECONNABORTED    = Errno(C.ECONNABORTED)
+	ECONNREFUSED    = Errno(C.ECONNREFUSED)
+	ECONNRESET      = Errno(C.ECONNRESET)
+	EHOSTUNREACH    = Errno(C.EHOSTUNREACH)
+	EINPROGRESS     = Errno(C.EINPROGRESS)
+	EMSGSIZE        = Errno(C.EMSGSIZE)
+	ENETDOWN        = Errno(C.ENETDOWN)
+	ENETRESET       = Errno(C.ENETRESET)
+	ENETUNREACH     = Errno(C.ENETUNREACH)
+	ENOBUFS         = Errno(C.ENOBUFS)
+	ENOTCONN        = Errno(C.ENOTCONN)
+	ENOTSOCK        = Errno(C.ENOTSOCK)
+	ENOTSUP         = Errno(C.ENOTSUP)
+	EPROTONOSUPPORT = Errno(C.EPROTONOSUPPORT)
+	ETIMEDOUT       = Errno(C.ETIMEDOUT)
+
+	// Native 0MQ error codes.
+	EFSM           = Errno(C.EFSM)
+	EMTHREAD       = Errno(C.EMTHREAD)
+	ENOCOMPATPROTO = Errno(C.ENOCOMPATPROTO)
+	ETERM          = Errno(C.ETERM)
+)
+
+func errget(err error) error {
+	eno, ok := err.(syscall.Errno)
+	if ok {
+		return Errno(eno)
+	}
+	return err
+}
+
+// Return Errno as string.
+func (errno Errno) Error() string {
+	if errno >= C.ZMQ_HAUSNUMERO {
+		return C.GoString(C.zmq_strerror(C.int(errno)))
+	}
+	return syscall.Errno(errno).Error()
+}
+
+/*
+Convert error to Errno.
+
+Example usage:
+
+    switch AsErrno(err) {
+
+    case zmq.Errno(syscall.EINTR):
+        // standard system error
+
+        // call was interrupted
+
+    case zmq.ETERM:
+        // error defined by ZeroMQ
+
+        // context was terminated
+
+    }
+
+See also: examples/interrupt.go
+*/
+func AsErrno(err error) Errno {
+	if eno, ok := err.(Errno); ok {
+		return eno
+	}
+	if eno, ok := err.(syscall.Errno); ok {
+		return Errno(eno)
+	}
+	return Errno(0)
+}