Bump Libcontainer to latest head

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

@@ -2,14 +2,14 @@ package stacktrace
 
 import "runtime"
 
-// Caputure captures a stacktrace for the current calling go program
+// Capture 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
+		prevPc uintptr
 	)
 	for i := skip; ; i++ {
 		pc, file, line, ok := runtime.Caller(i)