go.mod: require go-delve/liner instead of peterh/liner (#2905)

Use of `replace` in go.mod breaks delve installation using
`go install`. (see https://github.com/golang/go/issues/40276)
Workaround this limitation by explicitly require the fork
github.com/go-delve/liner.

go-delve/liner@v1.2.2-1 already has go.mod module name fixed
to be github.com/go-delve/liner.

Fixes go-delve/delve#2904

vendor/github.com/go-delve/liner/unixmode_solaris.go

@@ -0,0 +1,22 @@
+package liner
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+func (mode *termios) ApplyMode() error {
+	return unix.IoctlSetTermios(unix.Stdin, setTermios, (*unix.Termios)(mode))
+}
+
+// TerminalMode returns the current terminal input mode as an InputModeSetter.
+//
+// This function is provided for convenience, and should
+// not be necessary for most users of liner.
+func TerminalMode() (ModeApplier, error) {
+	return getMode(unix.Stdin)
+}
+
+func getMode(handle int) (*termios, error) {
+	tos, err := unix.IoctlGetTermios(handle, getTermios)
+	return (*termios)(tos), err
+}