Switch to new vendor directory layout

Fixes #113

Signed-off-by: Marcos Lilljedahl <marcosnils@gmail.com>

vendor/github.com/opencontainers/runc/libcontainer/stacktrace/capture.go

@@ -0,0 +1,27 @@
+package stacktrace
+
+import "runtime"
+
+// Caputure captures a stacktrace for the current calling go program
+//
+// skip is the number of frames to skip
+func Capture(userSkip int) Stacktrace {
+	var (
+		skip   = userSkip + 1 // add one for our own function
+		frames []Frame
+		prevPc uintptr = 0
+	)
+	for i := skip; ; i++ {
+		pc, file, line, ok := runtime.Caller(i)
+		//detect if caller is repeated to avoid loop, gccgo
+		//currently runs  into a loop without this check
+		if !ok || pc == prevPc {
+			break
+		}
+		frames = append(frames, NewFrame(pc, file, line))
+		prevPc = pc
+	}
+	return Stacktrace{
+		Frames: frames,
+	}
+}